Bad Customer Service

My son in the UK is desperately trying to contact Discovery Bank to assist and direct him in settling and closing his credit card. He has called all Discovery contact numbers from the UK, constantly holding on for hours, continuously pushed from pillar to post. I have even been into the bank but told only the account holder can call. The customer service seems non existent, we are at the end of our tether and desperate to speak to a manager or someone that will make this happen.