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On page 107 of the DND 5E players handbook there is a labeled area called "Spells known of first level and higher", in this section it says "when you gain a level in this class, you can choose one of the warlock spells you know and replace it with another spell from the warlock spell list, which also must be of a level for which you have spell slots.
I am starting out a new character as a warlock, and I thought well what are cantrips if not spells. I saw that on this answers forum it says in the DND Rulebook that cantrips are level 0 spells.
If they(warlock cantrips) are spells does that mean I can upgrade my 2x0 Level cantrips to, lets say 2x2nd level spells or can you not upgrade cantrips to higher spell slots?