Do I have to have cellular service to factory reset my phone?

I have an LG K7 from MetroPCS. I later switched to T-mobile and had my number ported over. I would like to sell this phone, so I did a factory reset but forgot to log out of my google account first.

It asks me to log into my google account, which I can do, but then it wants to automatically verify itself by sending a text message to the phone, which doesn't work because my number is on a different phone now. Is there any way around this? I really don't want to have to pay for service on this phone just so I can reset it and sell it....

Get the text message on the other phone, look at the verification number (at the most, it shouldn't be more than 6 digits) and log into your google account.