no invoice and no one knows how much i still owe

I'm so tired of this network provider.. In February 2021 i wanted to upraged my contract with cell cell and i was told a lot of stories about an account i had with the 2001 and was settled in full. i asked my self how did i get all the upgrades after that one if it was an issue and why is it coming up now. Anyway i was fine with that and decided to wait for my contract to end which was day before yesterday 16 June 2021. last month i had to fight with customer service for them to send through my statement for May. i got it 2 weeks back imagine. i still haven't received my June statement and when i call the call center they drop they put u on hold till it gets dropped and they don't even know their work coz they tell me they cant locate my recent statement, they can only see until March 2021. No one can help whatsoever. i checked the cell c app they it says i owe R687 and that's total madness. they keep on telling me that their systems haven't update. i normally pay on the 20th and that's on Sunday and no statement no one knows how much i still owe. I'm done with this network provider and their *********** staff.. can i get clarity on my account please.