If you only have one credit card at a time, you only have to pay the €30 charge once per year. It's paid every April, or when the account is closed.
Ryanair Visa are correct in charging you the €30 government stamp duty when you close your account with them.
You should ask for an exemption letter from Ryanair Visa, and send it to UB when you get it.
When UB get the exemption letter, you won't have to pay the €30 duty again in April.