To get admission in MSc in Most NITs , process is through CCMN portal. here is the linkย http://ccmn.in/

EDIT: Now if you are a BE/BTech student and willing for MSc in mathematics then only NIT-Arunachal Pradesh among NITs is offering you MSc and that also not pure mathematics… ๐Ÿ™

If you are not getting any other institute for MSc then just participate in this counseling and fill all institutes which you like in choice filling… Then if you get admission in any NIT of your choice as per your choice filling , you have to pay fees (may be through DD or State Bank Collect). Then with receipt of paid fees and all documents you have to go to that respective NIT. When time comes to show your fee receipt and documents, they will notice that you are a BE/BTech student. The people who will verify our documents actually will not be aware of eligibility criteria and if they, just tell them that as you have studied Mathematics for Four semester you are eligible, since there is no special eligibility criteria like six sem study of math on CCMN portal… This worked for me last year at NIT Warangal…

I am sure that finally they will not cancel your admission… Stuck to your argument that since there is no special eligibility criteria, i am eligible…. ๐Ÿ™‚

And if they reject your admission you will get your money back as per refund criteria available on CCMN portal…