Those kind of SMS check usually ban voip providers. So you need a real line or a prepaid cellphone, and it can presumably only be used once or twice on this ser

Those kind of SMS check usually ban voip providers. So you need a real line or a prepaid cellphone, and it can presumably only be used once or twice on this service before the number is "burned". Such checks, although not perfect, do prevent a huge amount of spam and bots by having a very real cost for bots/spammers, and essentially no cost (other than their privacy) for the user.