Has your phone ever gone into a complete loop with pages opening and you trying to close them as they open. Watch out for this it can grab your details without your knowledge and then you will start seeing charges on your mobile bill that should not be there.
Firstly you can stop it from happening: ring your provider and tell them to block subscriptions.
If it is already happening then find out who they are, sometimes you will receive a text message each week, monthly etc. Use this text message to track them down and cancel it. Then get on the phone to them and threaten action against them to reclaim your money.
One such scam running specifically in Facebook Ads is the Bigmobau.com they will charge you $6.99 a week and it will appear as separate purchases on your mobile bill. Check your bill if you are receiving these charges and question your mobile provider billing department.
I myself have had this scam run on my mobile and it is something that can be ignored as you think how can someone be charging additional money to your bill without knowledge, but apparently they can if you do not block it with your mobile provider.
If you have any questions on this matter please contact me or leave a comment.