Worst service to close account

I will NEVER recommend RCS, worst interest rates and you struggle forever to close the account! They take hours to answer their phone. Struggle to close account. I requested a settlement letter and paid the account in full. The technical service assured me that I am done with the account, I will not receive another invoice after paying the due amount. Afterwords I received communication stating that my account is in arrears. I phoned them twice after this and they said they will reverse it. After the second time I insisted that they send me a letter to prove my account is paid. I received the letter to state that I owe nothing. All the way they promised that they are busy closing my account and that it will take a few weeks. Now again I received a sms stating that I had to pay my account.