One thing is to install a data cap on your router. I dunno how to go about it sadly but I do take screenshots from my router page. It's way less than what those morons tell at ACT.Similar thing happened to me but with BSNL. Their record didn't match my usage, like at all. I raised a complaint but didn't know how to prove it. Their office employees are all clowns. I even met the GM and the AGM but it was useless.
If someone knows a tip or two I'm all ears. I don't know how true this is but theu said the server is in Kolkata. If possible I would like to get the raw data usage info directly from their server.
They have just started putting in Jio lines in my locality. Being a t2/t3 town I honestly am not sure how good it will be despite their assurances.