MTN data failure / unsatisfied customer!

Good day,

I took a contract of 5GB Aug 2018 and it has been ok until July 2019 when data was loaded on the 12th and disappeared on the 16th i had a funeral to attend to i did have time to attend to it immediately but eventually i called 135 wanting to know why and that they must send me proof that i have used the data they said they cant send me usage until month end. Just when i was going to the store to get the usage, Aug 12th new data was meant to be loaded so i waited for it and to my surprise according to MTN it was but it again was apparently finished 13th Aug 16h45 by my phone internet. So i went to the store asked them how come whole 5GB gets finished within a day (or few days for that matter) when there has been no changes on my usage. I went to Stoneridge Mall 14th Aug to query asked them to send me usage they agreed and the sales agent Lulama took my email address. I then followed up 17th Aug as there was no feedback yet and they told me according to their investigation i was given data and used it and that i have to write a letter and send ID copy and i asked why wasn't this information requested at the store as i could have provided and avoided more delays as i am without data and on their side they are telling me they are still investigating. It is so unfortunate that MTN is hiding behind iPhone saying its background are active and taking up data unaware even though i told them i have no active apps and what is worse the store manager on duty (Victor) at Stoneridge went through my phone and couldn't find any app / apps that were active that could be taking off my data, question is where is the data why blame on apps - why MTN is doing this all of a sudden and why cant they just send the usage to the customer why ask written letters and ID copies when i was at the store prolonging the already daunting and frustrating experience the customer is dealing with? Ref for the call: *** and trouble ticket number: ***. This is frustration, please assist urgently!!!