Diners Club Pathetic Service

I have had a Diners Card since the early 1980's. I have not used it much lately because of the loyalty programme with my bank. I have recently had a major fall out with my bank regarding the rules being changed and have asked Diners Club to increase my limit as it has not been changed for years. I have sent three emails and made three phone calls over three weeks now. I am told that someone will be in touch but I never get a call back. I cannot believe that they can treat previously loyal customers with such contempt especailly where you are trying to give them more business.