Oh no fuck that, business 101 is make sure that your checkout page works. There is plenty of competition in this sector, take your money elsewhere.
You can get a phone number online for a few dollars.
Historically those are less useful because some of the verification systems require a real phone number and that your name is associated with the account, depending on what and how they verify. It's annoying, I use a google voice number as my primary, and it often gets rejected.
Good2Go is $5/mo for a real SIM with unlimited talk/text + 1GB data.
There are several tiers to these services, some are selling real us phone number verifications at about 0.5usd/text while others are selling virtual phone number verifications at much cheaper. From some limited experience with the former, there is rarely if ever any problems with rejections.