Poor service and bad attitude

My mother has a contract with RMCS and has been using the number for years, now she wants to cancel the sercive but they are giving her a hard time. weeks after weeks they have been saying the contract will be cancelled in 48 hours but till today it has not been cancelled. she has been calling from the Jet store and was told again that the it has been cancelled and received an sms with reference ********** 77945 this was sent to confirm that it is cancelled on the ********** 791 number she is using. please advice on what she can do. They do not vaue their customers and the customer service is very poor with call centre agents that have bad attitude. Your assistance will be highly appreciated