Deposit withheld with no reason and no communication

They took the booking money and the deposit money in less than a minute, but it has been three weeks, and the deposit has not been returned although the car was returned with no damage or addition cost that would apply. Dialing the CallCentre results in no answer, the link on their Email re the terms for the "authorization hold" leads to a page that does not exist. Im sure I will receive the deposit back as soon as that received the interest on it.