Hi peeps, some more advice:
In the United States, area code 900 is a "fee-for-service" also known as a "pay per call" area code. Back in the 80s/90s most people associated these with phone sex lines. If you called it, it would be the same as calling a long distance number or calling without any free minutes on your cell phone plan and paying a VERY hefty amount, sometimes as high as $2.00 or more per minute, to be on the phone.
I have caught an instance on FindWhoCallsYou where an Indian scammer placed a phony report about a Microsoft scam and the phone number is in the 900 area code. This can be one of two scenarios:
Plenty of people like myself called 900 numbers (there were a lot of services besides phone sex, like video DJ requests or Nintendo game cheat walk-thrus you paid to listen to) and got into big trouble with their parents when they got their phone bills. You could also buy products using 900 numbers and using your phone bill as a cheap way of becoming a bill-me-later credit card since you would eventually pay the bill.
In your case it will be your VOIP provider demanding payment if you don't have the credits, if your VOIP carrier will even allow you to make calls to 900.
Do not ever call the 900 area code.