Many classes: bard, ranger, sorcerer, and warlock have this type of text in their Spellcasting or Pact Magic feature under Spells Known of 1st Level or Higher:
Additionally, when you gain a level in this class, you can choose one of the spells you know and replace it with another spell from the spell list, which also must be of a level for which you have spell slots.
Can I choose to replace cantrips or only spells of 1st level or higher?
*Unless you use optional rules from Tasha's Cauldron of Everything, see down below.
Spells Known of 1st Level and Higher [...]
Additionally, when you gain a level in this class, you can choose one of the spells you know and replace it with another spell from the spell list, which also must be of a level for which you have spell slots.
For the sorcerer, ranger, bard, and warlock the sentence above is under the section Spells Known of 1st Level and Higher.
The phrase must be interpreted with that context. When read this way it is clear that when it says "one of the spells you know" it is implied that it means only those 1st level and higher. There is a cantrip section immediately above that one which does not have any such wording.
Additionally, the phrasing implies that both the spell to be replaced and the one that it is being replaced with must use spell slots:
you can choose one of the spells you know and replace it with another spell from the spell list, which also must be of a level for which you have spell slots.
The implication being that the spell that is being replaced is already at a spell level for which you have spell slots. The reason they don't say this more explicitly is likely because of the context of it being under a section that is only talking about spells of 1st level or higher. And cantrips, despite being 0 level spells, don't use spell slots:
The first sentence of the rule on cantrips says they don't use spell slots. The rule isn't kidding.
This also seems to follow designer guidance/intent as Jeremy Crawford says explicitly here:
The sorcerer's Spellcasting trait lets you replace a sorcerer spell you know when you reach a new level in the class. The spell must be of a level for which you have spell slots, which means it can't be a cantrip; cantrips don't use spell slots.
Jeremy Crawford has also explained intent more generally:
Q: Is it possible at all to replace a known Cantrip with a different one? Or is that a permanent choice?
A: Learning a cantrip is typically permanent. A DM could come up with a story-based way to replace one w/ another.
The narrative reason for this is likely because cantrips are different from spells in that:
Repeated practice has fixed the spell in the caster’s mind and infused the caster with the magic needed to produce the effect over and over.
Jeremy Crawford seems to support this narrative as well:
A cantrip is special: it grows in power as you do, and it is magically bound to you. In most D&D worlds, that bond isn't easy.
Tasha's Cauldron of Everything includes new optional class features that allow for the swapping of cantrips. The exact method varies from class to class. For example, the Wizard's Cantrip Formulas says:
You have scribed a set of arcane formulas in your spellbook that you can use to formulate a cantrip in your mind. Whenever you finish a long rest and consult these formulas in your spellbook, you can replace one wizard cantrip you know with another cantrip from the wizard spell list.
The wording of the feature already shows why you can't exchange a cantrip:
which also must be of a level for which you have spell slots.
You don't have spell slots for Level 0 spells, which a cantrip is (PHB p.203).
For Warlocks, Bards, Sorcerers, Rangers, the paragraph heading addresses Spells Known of 1st Level and Higher. You thus can't replace a cantrip under that rule of "spells known" changes since it isn't a 1st level or higher spell (and also because you don't have spell slots for cantrips).
Cantrips
A cantrip is a spell that can be cast at will, without using a spell slot and without being prepared in advance. Repeated practice has fixed the spell in the caster’s mind and infused the caster with the magic needed to produce the effect over and over. A cantrip’s spell level is 0. (SRD p. 101; PHB p. 203)
This is also addressed in the Spellcasting chapter, under Spell Level:
Every spell has a level from 0 to 9. A spell’s level is a general indicator of how powerful it is, with the lowly (but still impressive) magic missile at 1st level and the earth-‐‑shaking wish at 9th. Cantrips—simple but powerful spells hat characters can cast almost by rote—are level 0 (SRD. p. 101, PHB p. 201).
Furthermore, cantrips don't occupy any spell slots. From the text you cited:
Additionally, when you gain a level in this class, you can choose one of the spells you know and replace it with another spell from the spell list, which also must be of a level for which you have spell slots.
It is fair to say that cantrips exist as a separate category of spell than the spells of level 1-9.
There is no provision in the rules for casting cantrips "at higher levels" as some other spells can be cast. Cantrips are treated differently in a lot of ways than known spells, or prepared spells. For example, a cantrip's casting level is driven by a character's level, not the level in the class of the character. For example, if you are a Warlock 7/Paladin 4 or a Warlock 11, you still cast the cantrip Eldritch Blast at 11th level.
The spell creates more than one beam when you reach higher levels: two beams at 5th level, three beams at 11th level, and four beams at 17th level.
You don't expend a higher slot to get a higher level magical effect, as you do with spells of level 1-9.
Within the Tasha's Cauldron of Everything sourcebook, each spellcasting class is granted the ability to change cantrips. The method varies from class to class. For example, wizards have the ability, called Cantrip Formulas, to change one after every long rest:
You have scribed a set of arcane formulas in your spellbook that you can use to formulate a cantrip in your mind. Whenever you finish a long rest and consult these formulas in your spellbook, you can replace one wizard cantrip you know with another cantrip from the wizard spell list.
The other classes tend to have a new feature that allows for them to change either a cantrip or multi-version class feature at each ability score improvement. For example, Sorcerer's Sorcerous Versatility:
Whenever you reach a level in this class that grants the Ability Score Improvement feature, you can do one of the following, representing the magic within you flowing in new ways:
- Replace one of the options you chose for the Metamagic feature with a different Metamagic option available to you.
- Replace one cantrip you learned from this class’s Spellcasting feature with another cantrip from the sorcerer spell list.
These are optional rules, however, and require a DM's approval to use.
