Worst customer service ever

Worst customer service ever two years ago I received a call to be told that I can get a Huawei phone for 99 per month I agreed and when the phone was delivering it was not what was advertised to me ,and told Mr price that I don't want the phone and that the phone should be collected.The phone was collected and now I am handed over for the same phone that was collected.I receive threatening sms and emails saying that I will be handed over and when I call I am told that the account has been settled,I then ask for a settlement letter instead they continue to.send me the threatening sms.Honestly what to I do in this regard. I never ever used the phone.You assistance will be highly appreciated.