Revenge on the Indian Call Centers

You either!

I say nahin dhanyavad and hang up, they don't call back

A soon as I recognize one of these calls, I start pushing a few of the numbers, a second or two apart.  Each number has it's own individual "beep" sound...any number sequence is OK and keep it to just a few. Then I interrupt the caller and say.."just ignore those beeps, all my calls are traced and recorded". Say no more, stay silent and immediately the calling party will hang up.  Works every time. (Note: There are times when my calls are recorded.) Of course, if I can I report the number as a SCAM.

I would not be answering unknown numbers, because you do not know if you will be charged for the calls.  If they are actually calling from other country, you could be charged on your phone bill for the call.

Can you provide a link to a story about such charges being made?
Where the calling party can automatically, without authorization, charge your phone number?

slg is absolutely correct, cramming charges to your phone bill is most definitely a reality:
Inbound Cramming

Nice...an 18 year-old article.

It's still relevant, unfortunately, as scammers are always trying various dishonest methods of getting money.
Knowing what was done in the past helps us to understand how to get our money back and get government agencies and the courts to put a stop to new scams.

I know what cramming is; I have had to refute unauthorized charges in the 1990s and early 2000s.
There is nothing in that link that answers my question.

"sig" makes a vague statement without any explanatory detail. My question is specific. Here is my thinking :

a. If I make a long-distance call, my phone number will be automatically charged for the cost of the call.

b. If  I make a call to a 900-number, my phone number will be automatically charged whatever the jerk who owns it wants to charge. I know that will happen.

c. When I make a call to a foreign country like Jamaica, my phone number is automatically charged international rates.

I interpret what "sig" says to mean that if I pick up my handset, say hello, then hang up my phone, the calling party might automatically be able to charge me for the call.

I am NOT asking about cramming; that is fraud. The calling party (or its co-conspirators) have to send a bill to my telephone service provider. There is nothing automatic going on.

Here is an analogy : If your doorbell rings, don't say anything, because whoever is outside might lie to you.

=== See how vague that is?

True. Back in the 1990/2000's one of the telemarketing scams was to call a business "to verify your information". They would want name, address, and the name of your phone carrier (like any customer really cares about that). With that, they could cram charges on your bill, and most likely record/edit the call to make it sound like you agreed to something. But I think that's the closest example I can think of where if you answer your phone, you would get charged...

Kept gettin the windows call. One day, In my best indian accent I say, "oh my gosh, only God and save me now!" he hung up and sopped calling.

When I get one of those computer error calls, I tell him that I don't have Microsoft windows, I have Andersen Windows.  Usually there is a pause, followed by a string of finely crafted obscenities......

I pray to the late Jagadguru Kripalu Parishat for divine guidance. While I was in a deep meditative trance Kripalu spoke to me saying that we must be kind and forgiving of our foes. Forgive, forget and move on.

Stupid shill. Keep your lying "religious" crap to yourself.
We will not forget.
To us, "move on" means to move on the criminals that run these operations and taken them down.

I prefer to give Karma a little help.