Can't verify phone number

I have been trying to log in to my credit union account online, but in order to do this I need to verify my phone number. However the verification codes are not reaching my phone. This issue has gone on for weeks with the credit union blaming my phone company for the problem, and vice versa. The phone company thinks the problem is with the way that the credit union is routing the message, and this seems most likely to me, but the credit union insists it's not their problem. Surely they have an obligation to provide me with proper access to my account.