‘When swapping out of a contract, you can usually Avoid losing your number by “Porting” your number Before the Actual Transfer. However, the porting process is entirely under the jurisdiction of the carrier and is beyond our control. Porting policies seem to change very often with each carrier. Therefore, we suggest that to get a definitive answer to your question please contact your specific carrier. ”

But of course, if you were really interested, I would suggest calling cellswapper.com’s number (I think they even have live chat) and asking them directly how it would work in the case where the number couldn’t be ported.