I had gotten taken in by these folks a couple years ago, and afterward got nervous and changed all my passwords. Since then, although I have told them to stop calling me, they continue to do so randomly, and always from different numbers (as in, searching the numbers in Google always brings me back here). The callers get very belligerent, and I end up each time saying "Please do not call me again and I am going to hang up now" and disconnecting -- at which point they try calling back two or three times (and once tricked me by using a different number). This request for bank information for a refund has come to me twice now, and I've taking them as far as getting to the Teamviewer site, as which point I refuse to enter anything. I tell them that if they are a legit business they will send me information in the mail. That of course does not work.
DO NOT GET INVOLVED WITH Omnitech. They are big time scammers and they are in India. They want to take control of your computer, steal your information and install virius and malware on your computer so they can assess it any time and you don't know they are there. If you gave them your credit card number, change the number immediately because they keep trying to access your acct.
If you got the Microsoft phone number off of the internet they are the ones who probably the phone, Omnitech claims they are contractors of Microsoft and will tell you any lie you want to fall for. I finally got ahold of Microsoft and they are aware of the situation. Microsoft tells me they do not hire contractors and they do all the work in house.