Thanks for your post and welcome to our community.
So if your wife is the account holder then when she took out the contract a credit check would have been done on your wife and the payments should come out of her bank.
If you wanted to change it into your name this can only be done if you're not within a contract term. We'd then change the number to PAYG and run a credit check on you to be able to pop the Pay Monthly services back on. We'd also have to have the payments coming out of your bank moving forward.
If this is something you want to do it will need to be done by speaking to the team on 789 or 0345 6000 789.