Well you could try this ...
https://www.hark.com/clips/qlztssnyzk-telemarketer-calls-murder-scene
I usually answer and give them a run around. Normally I answer the phone and tell them I am a friend just visiting but that the person they want to speak to is in the garden, I ask if they would like me to call the person in. Normally they say yes so I go to the hallway and shout 'hey someone on the phone for you' and tell the caller they are on their way. Leave the phone a couple of minutes and see if they are still there - if yes I tell them its a very long garden and to hold on as they ARE coming. I just see how long they will wait for - the record is about 15 minutes. We have a sort of uinofficial score in the house to see how much of their time we can waste.
Theres loads of ways to turn it into fun - pretend your Winnie the Pooh and ask for a loan to buy Honey
Pretend your HAL 9000 from 2001 - I'm sorry Dave I dont think I can do that.
Tell them you have a super bad gambling habit and have the mob on your case - can they lend you a few thou fast to save your fingers from being cut off.
The possibilities are endless to have some fun with cold callers.
I sometimes pretend that there are two of in the flat with the same name - oh you want that Ms Smith - hang on I will get her. Hello MS SMith - oh I am sorry you want the other on - hang on I will put her back on the line - and so on.