I tried most of what you listed twice and it had no effect; they actually started calling more. What did work was telling them I used my contacts in the FBI to get a trace on their location and I knew who leased the space in the building they were calling from. That got their attention and presto - no more calls.
There’s an audio out of a guy who always answers these calls by saying that the person they are trying to reach has just been killed and that he is a member of the local police and needs to know how the caller knows the decedent and all of his contact info so that they can send a member of the local police where the telemarketer lives to interview him. It’s a riot!