Unknown and never-sent outgoing text messages

For the last few months I have to pay for some outgoing text messages to Dominican Republic and the phone number is 849 755 32975 which i never sent. I don't even have such a number inside my contact list and i can not find or see any of these messages inside all my message histories, and see what messages being sent to this number.

The only way I find out this problem is to look into my monthly phone detail usage bill. I talked to Bell phone company provider a few times. They could not help me about this issue since they are outgoing text messages they could not block them.

How could they use my phone to send these messages that I could not see and have any control of?

I need your help on how to stop it before it becomes a more serious problem and out of my control, please.

Thanks a lot. K.S