It's out of our hands
As the cryptocurrency industry continues its climb towards worldwide adoption, banks have to consider the possibility that they will gradually lose the influence of their clients' funds. Lately, the card associations have added additional fees for cryptocurrency transactions, while some banks have outright banned cryptocurrency purchases made by their customers.
Furthermore, in the wake of the December 2017 hype, customers started spending using credit on bitcoin assuming the price would increase. This poses a credit risk for the banks, who in turn considered the activity as gambling on the cryptocurrency rate.
What you can do about this
If you're using the services of a bank that has a ban on buying crypto with a credit card, you're more likely to succeed when using a debit card. It may also work to call your bank directly.
As crypto enthusiasts, we at Coinmama have faced similar issues and some of us have decided that we will not let our banks dictate how we should spend our money. However, while changing your bank should solve the issue, we also understand that this is a big decision that should not be taken lightly.