Simply, easily, trivial. With just a little effort. Try again often, try again later. No problem, to appeal, the process, Mr.Kafka, all you have to do is, be seen by two witnesses, to uphold your interest in.. Of course, if that is to complicated, and the nuances of the wording, are a endless stream of passive agressive insults to your intelect. Noone can help you, because there is noone home. The company you are trying to reach, consists of a algorithmic amobea, and would like to connect you with other concerned customers, so that you can all support each other in these difficult times, created by this difficult company.
Those temp SMS numbers used to work, but now the places that require a phone number seem to be sharing notes and block them (they'll accept it, but never send a text). This is similar to how places that require an email address have gotten pretty good at blocking many of the temporary email providers (they'll accept them and just never send you an email).
Just give them a fake telephone number: https://receive-smss.com/