Cellphone number delima

I've been trying to change my cellphone number with Bankmed for over 6 months now. I no longer use the number that's provided on their system and I've tried to change this numerous time with them but it still hasn't changed to date. I cannot changed anything online because the OTP goes to the previous number which is something I am very uncomfortable with considering the ********** activities that are doing the round. I called the contact center to changed my banking details and was told to do so online however when trying to do so the OTP went to the previous number AS ALWAYS................ Bankmed sort this out ASAP. This is seriously frustrating!!!!!!!!!!!!!!!!!!