Trying to move but not getting OTPs

Been a customer for about 18months loyalty paying. Just want to change my address. Keeps trying to send me an OTP but I never receive it. Phone the call centre twice wasting over 1hr45m waiting, only to be told they can't help me without the OTP. My phone number hasn't changed in 20yrs and not with them so I don't understand why I'm not getting the pins. I am now paying for a service I'm not getting!