If they made you to pay (that Rs1200), they may get Rs120 as commission, I guess...
If you are really not busy when they are calling, you can just use their threat as time-pass. They are acting as threatening, you can act as frightened and continue their call and never allow them to disconnect as far as possible. Once they find out that, actually you are the one who is trolling them (and NOT other way around) they may never call you back.
But please remember one thing, RCom is NOT fool to go to court for Rs1200/-, even their lawyer will charge more for each session. Further if the case turns out against them for whatever reason, they will be penalised heavily by courts. So BE SURE, they will NEVER go to court. They just transfer such cases to collection agent and they will be ready to pay huge commission (about 10 to 25% or more -- whereas in normal cases dealer gets 3.5 to 5% commission in prepaid and 1.5% MAX in postpaid) if customer pays those dues after such threats. So those collection agents are trying their luck.
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Following is what happened in my case few years back...
One such collection agent called my friend for almost exact case like yours... But I attended that call..
Man: Hello is it Mr.X? [My friend's name]
Me: Yes...
Man: Sir, we are calling from court..
Me: Dai Senthil, how are you.. long time, no see? When are you coming to Bangalore? [My friend is actually in BGL] Why your voice is different? Have you got cold?
Man: Sir, we are calling from court for the amount you need to pay to Reliance..
Me: Dai Senthil... I won't believe your prank this time.. Last time was something..
Man: Sir, we are NOT...
Me: Dai, don't act smart.. Last time you called from your boss number and you get caught while we are talking.. Remember?
Man: Sir, this is a serious issue... You NEED TO PAY..
Me: Dai, I know you are now calling from PCO for safety.. Better luck next time buddy.. BTW how is your mom?
Man: Sir, will you please stop it? WE ARE FROM COURT. A CASE IS FILED AGAINST YOU FOR NON-PAYMENT OF RELIANCE BILLS..
Me: (act like frightened a little) Sir, you are really from court?
Man: YES, WE ARE (A pride of victory in his voice)
Me: Sir... Sir... I have not done anything wrong sir... please sir... Its Reliance fault sir..
Man: Now nothing can be done.. You are going to jail for non-payment
Me: Sorry sir.. I will pay in court itself sir... Please tell the bus route sir..
Man: So you are ready to pay, right?
Me: Yes sir.. I have Bus pass.. I will come without fail sir..
Man: You can pay by
Me: Sir, whether we play singles or doubles sir??
Man: WHAT?
Me: Sir, you asked to meet in Tennis court. I am asking about the match there sir...
Man: Are you making fun of me?
Me: Yes sir, from the very beginning. You are too late like Tube-Light sir..
Man: YOU ARE GOING TO PAY FOR THIS... THIS IS A SERIOUS LEGAL CASE..
Me: I need not pay as I have BUS PASS to Tennis Court, sir..
That Man disconnected the call, may be even banged his head on nearby wall for wasting money and time for this call...
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This is one example... There are numerous possibilities...
Life is short and do NOT waste it for unnecessary fears... Instead make fun of those time, have a great laugh, that is good for healthy life..