Miss treated and abuse

I have a mobile contract with Telkom that i took from Telkom @ Nyanga Junction Guguletu Mid Feb.

Im totally not happy with the service i get from the store must special the manager.

I took a double deal of Huawei Nova Y90 for me and my son. My son notice that after3 weeks having the phone when he is on whatsapp the phone will just go to email, games, Facebook. I went to the store to report it they confirm its a software issue. They advise me to send it back to the with everything nd i did that After a 2weeks i receive sms that stating i must pay 500 for repairs and 500 for service fee. I went back to the store since I was not happy about the sms i received cos my son only used the phone for3weeks and i was thinking that as they ask me to return it will do an exchange but when i went to the store and ask about the situations i was told insurance will take place after6 month installment but i was not informed at the store when i brought the phone but that its not an issue how come i pay for the phone that has software issue cos my son did not do that on the phone its manufacturing fault im writing here now since im not getting help from the store last time I was at the store the manager drop the call while i was busy explaining what frustrated me it's that i wanted to canceled the contract but i was told buy the manager Telkom will blacklist my name and I'm paying for the second time the phone that my son his not using. Please help me.