airtime billed without my concern

i received an sms that states that my number was selected and has won an S6 cellphone it looked like the sms was from mtn and there was a link that i was suppose to click to be redirected to claim but what was amazing was when i clicked on the link it redicted me to the mtn site where i had two options whether to agree or declined to pay R7 per day so i declined because i couldn't understand how is it possible that i have won then have to pay R7 per day, and the next day i topped up my account with R15 and make a single call but after that call my airtime was gone and on the 14th mtn topped up me with R110 airtime and i only made two calls and my airtime and data was gone that's when i called mtn to seek clarity and they told me i have subscribe with smartcall and they gave me a number to remove my number but when i checked with the company that they should send proof that i have gave them permission to credit my account they say number was stopped, which is me who stopped it, now i want my airtime because i didn't agree that they should credit my airtime.<br> <br> please help