BAD SERVICE FROM DISCOVER BANK!!

We are trying to cancel our credit card. It has taken 4 phone calls to Discovery plus the stupid questions to verify that it is the right person. The card belongs to my husband yet he is 76 years old and not well therefore I assist him. Yet they do not accept this....The problem is Discovery have his old cell number and new cell number on there system. Yet we no longer have his old cell phone, This has caused a major problem. We spoke to them on Friday for 2 hours and today 30min and NO SERVICE!! The problem has still not been sorted!! So I must phone them again!!