I had received a call from kdt captcha company which offered me to do 10, 000 captchas and submit it within 10 days from which i'll be paid 22, 000 rupees. I started doing the work and the next day i had a couple of doubts regarding letters in the captcha which i wanted to clarify with the agent. I called the agent and she never picked my call. I sent a text in their whatsapp number, the lady saw the message and never responded. At that moment, i texted them to terminate my id and i'll not vale paying them. Today i received an sms and call that since i never completed the work, i should pay 5000 rupees to the company. I mean, why should i pay to this company who couldn't even clarify doubts of their consumers? Was this information helpful? | 
please do not be scared and don't let these people harass you by any means whatsoever.
This is a scam which will make you pay 5000 rupees to these fraudsters by just making you believe that you have done something wrong and by creating an element of fear, for example, the stamp paper.
There are very specific things written in contract law of India, one of them is void contracts and voidable contracts.
The very contract which is not enforceable or can become unenforceable through the process of the contract cannot be enforced.
Like you said that the count of the captcha goes back to 1 after every certain time, this contract cannot be enforced to its 10000 limits and hence becomes void or voidable.
Next, even if all this was legitimate, you don't need to worry. but in all aspect, this is fraudulent activity.
The picture you have provided of the stamp paper has no clear serial number on it.
You can check the authenticity of a stamp paper by quoting the number mentioned on the stamp paper to the security press of India. The number you can find printed in black ink on the coloured portion of the stamp paper.
If there is no number, it means the stamp paper is older than the time when Govt of India directed to number the stamp papers That was sometimes in 2005.
So, the next time these people try to call or text you, ask for the serial number of the stamp paper they have provided and check its authenticity.
Please do not pay any money to anyone in fear or uncertainty. Always clear your mind and facts before you cash out your hard earned money.
Hope this helps.