Honestly, from my little knowledge about smartphones, I can tell you that the problem is not that serious. However, have you tried to use a temp sms uk for verification at https://quackr.io/temporary-numbers/united-kingdom? There is a slight possibility that this problem is caused by your phone and not your sim card. So you can try to use a temporary number. If it doesn't solve the problem, I suggest you consult a GSM service. Those guys are professionals in this field, so I am sure they will know how to solve your problem.