Bad service

On the 1 March 2019 I registered a letter from Carlton Centre Post Office to Bryanston Post Office. I've calling them but nothing is happening. The person who was supposed to those documents has been calling me. They did went to check it if it's there but they never got it. I've been calling them they are so rude nothing comes out from them. It was there since 06 March but the receiver has not received it. I will never used or trust them. I called twice this morning they were very rude explaination what to do still the letter is with them. I advice to use courier services more than the post especially Bryanston Post office in Johannesburg(Jozi)