I do not agree to terms and conditions
There were a few telemarketers who do not relent until you say a yes, it does not matter you report to them to the authorities they change the number and keep calling you again and again and again until you accept the offer.
My experience of dealing with a few. This was when people were getting new numbers when moving to another city as the numbers were not portable, so you cannot ignore calls coming from new numbers. I had to walk out of meetings for the call or call back numbers that I have missed just to be annoyed by a credit card representative.
One evening I decided to put an end to this one, I accepted the offer and asked to send a representative. When the representative turned up I declined to sign saying that I do not accept the terms and conditions but I still want to have the credit card. The representative was very annoyed, I felt sorry for him but was determined to do it anyway. I repeated this only thrice and the calls came down to zero.
Next ones were the personal loans, I expressed eager interest in it and asked some questions like, “Will you send someone to my home if I don’t repay?”, “How long will you wait before you send some collection agents?” and so on. The personal loan calls stopped immediately.
With TRAI DND it is very much controllable nowadays so not much tactics needed.