MBD not refunding money due to me!!

I was paying MBD for an account, and discovered in February that the account was paid up in June 2019 already, but was not notified by MBD that account is paid up and not further payments is required. I had to send them proof of payments, in order for them to arrange a refund. Since all documents was submitted, still no refund that is due to me. All documentation was submitted 25 February, and till now no refund. I have been trying all afternoon to call them, but the phone is either not being answered, or they put it down without taking the call.