Write a letter of complaint to the bank's customer service department outlining the problem, and the interaction you've had with them. Phone calls are fine if you make progress, but you have no formal record of their responses, which have been useless. If the same trail of incompetence was visible in a written conversation, you'd have them very embarrassed by now, or shortly about to be. Some sort of compensation would not be unreasonable too, but without the written evidence, you won't have this opportunity.
If they fail to deal with the written complaint, you can take the issue up with Visa or Mastercard. They hate getting drawn into this kind of thing, but if they feel the bank is failing the end customer, they'll kick them into action.