When I lost it with Tele2!

Today I received I guess the 15th invoice from a Telephone Company called Tele2 and I phoned them for at least the 25th time saying the same thing over and over again. You have promised to cancel the telephone subscription and you always say that I will not get anymore invoices but you always send me yet another invoice. So, I was not nice. I yelled and asked what do I need to do so you stop sending me invoices!? I have had this problem since May! It is 5 months now! You just promise me that there will be no more invoices by they keep on coming! I am so damn tired of this! Really tired!!!! I asked to speak to a manager as I could not take it anymore. The manager apologised and said that they will write me a letter confirming that no other invoices will appear....well you know me by now...I would not be surprised if Tele2 sends one again.