You're correct, which appropriately enough is why you're downvoted. The letters were placed on telephone dials when telephone ‘numbers’ used a mnemonic exchange+digits format¹, so there was no requirement to include the entire alphabet. Advertising mnemonics like the one in the grandparent comment came later, and entering arbitrary text such as names, which actually requires the whole alphabet, much later.

¹ https://en.m.wikipedia.org/wiki/Telephone_exchange_names