Vodacom take R20.00 per day without permission

Please let Vodacom stop taking R20.00 from my Vodacom phone== I belong so many years to Vodacom I do not hope this incident will let me change from service providers<br> I would like them to reimburse me I received the message on the 01/11/15 if I wish no longer to continue I must reply ''stop''=== who gave them permission in the first place to take of the money?? please help me regarding this matter<br> thank you <br> Lyzinda Joynt