Spend Increase without My Approval!!!!

So two days ago telkom smsed me to offer me a spend increase from my current 399 to 500. the sms read that if you were interested to reply with a yes or if not interested reply with a NO. I sent through 2 sms's stating NO as I know what I can afford and what I can't. Today I received and sms stating my spend was increased to R 500 effective the 1st of August......How the hell is it even legal to do this. No means No when a man forces himself of a woman against her will it is ****. Please stop forcing yourself into my bank account! I have said I do not want my spend limit increased. Please cancel these fancy extras I signed in to a contract with a set limit and the option to purchase extra from my service provide which works for My pocket