No details shared by bank and wrong commitment

I applied for credit card last year. At the time of applying, the bank representative told me that I can convert my outstanding balance into equated monthly instalment (emi). After 6 months of receiving my credit card, I had some outstanding balance so I thought to convert my outstanding balance into emi. When I contacted standard chartered customer care regarding same they said this facility is not available on my card. They also said it all depends on offers which changes time by time(which no one told me at the time of applying credit card) and I should contact them after 6 months time. I again contacted bank after 6 months and they were saying me again to wait for another 6 months. They just keep on repeating the same statement and again they told me the same thing which they told me 6 months earlier. After that I registered my complaint to bank and they again made the same statement and on top of that they added due to bank internal factors I cannot avail emi facility. When I asked about internal factors they said they are not supposed to tell me the internal factors. There were lots of mail went by but nothing happened. Few days back I made one request to increase my credit limit as my salary has been revised and I had to apply for one exam and that can be done through credit card only. This time again they repeated the same statement that this offer is not available on my card and due to internal factors of bank this cannot be done at this point of time. When I requested to know why its happening just to understand where I am lagging behind in the criteria of bank, they repeated the same statement again, we are not supposed to tell the internal factors of bank to anyone. I really don’t understand what their internal factors are and why they cannot be transparent with their customers. This really made me frustrated and left me no option other that consumer forum. I need to know why they made false promise to customers which they don’t follow after selling their product. Also I need to know what internal factors the bank have by through which they keep on denying for every facility or request made by customer. On what grounds they say to customer they cannot be transparent to their customers.