Sphere — I am getting multiple calls from them saying I will be charged under various ipc sections for not completing the work on time.

As per the contract i had to finish my work in 15 days but due to some glitch in the application provided by the company i was not able to complete the work. I had even informed them about the problem in their application but they issued me a legal notice which is as below. Further to explain, i had even paid the fine of rs 7500 because they scared me with various legal actions they would take. But even after the payment i am still getting calls from them, in fact today only i got a call from them saying i will be charged under section 73 and 74 of ipc.
Mail sent to me on: jun 27, 2018, 10:46 am
We legal department of sphere hereby having your case for non submission of work. We hereby notify you that if these condition mentioned in your agreement comes under these categories then you need to make payment of registration fees to our client. If you don't make payment to our client as per an indian contract act 1872 section 17 shall be imposed on you for negligence of payment. We also want to inform you that section 420 of ipc shall be imposed on you for doing fraud with our client for non payment of registration amount which accounts to rs. 7501/-. Section 499 and section 509 for cyber defamation shall be imposed on you for defaming the name of company on internet. Section 66 a shall be imposed for using abusive words with our client and advocate legal firm. Section 15 of ipc for coercion if you coerce our client. If payment is not done then your case shall be transferred for further proceeding at an arbitrary court. An arbitrary and conciliation act of 1996 as per an article 14 shall be imposed on you and you might need to pay rs. 50000/ - for total loss to our client.

This would be compulsion for every client who breach this contract. So, please try to understand the situation and make payment to our client as early as possible. Our client is sole proprietor company and once you not make payment then an arbitrary and conciliation act of 1996 as per article 14 is mend to safeguard them. So, we advise you to cooperate and pay this amount as early as possible.

Your cooperation is required for making payment to our client or else you need to get ready to face for legal consequences.

Please make payment of rs. 7501/- = rs. 5200 agreement amount+ rs.2301/- noc fee please provide the screenshot of successful payment on this email id. On the basis of that we will provide you noc letter.

Thank you

Mail id: slenge. [protected]@gmail.com

I was provided noc certificate as well.
Currently i have been getting calls and messages from these numbers: [protected], [protected], [protected]
They claim to be as advocates.