Ah, the dreaded bead lock, my apologies. In that case borrow a time machine and buy tubeless tape instead, I started out when rubber bands were all there was and ditched them asap.
If you can’t borrow a time machine then the Pedros lever is probably your only hope.
Doesn’t help this time but different tyres have different tightnesses of fit, and you thought there were only 3 sizes 😉 Trial and error unfortunately, but as a rule of thumb you shouldn’t go over 40psi to seat a tyre…
Slosh loads of soapy water into the join of the rim and tyre and see if that helps to shift it, failing that put just enough air in it to stop the rim grounding and ride it in small circles on the grass until it falls off.
Good luck 🙂