Lost airtime

I have a contract with MTN and on two occasions in the last two months large amount of airtime has been disappearing from my cell phone.<br> I even discovered that someone else had the same number like mine.<br> I have tried on numerous occasions to get hold of a consultant or just somebody on the service provider line number (808) to inform them of my problem, but to no avail.<br> The mtn prompt messages plays and as one press the right option to speak to a consultant, it lets you hang until the voice tell you that all the consultants are busy and cuts you off.<br> How will I ever find out where my airtime has gone too.<br> I stick to my part of the contract by paying my monthly subscriptions and expect the service provider (MTN) to do likewise when I need them for a particular problem.<br> This is totally unacceptable