MTN Data disappearing and no service

I've been buying the 1GB weekly data from MTN and it keeps disappearing. I bought 1GB 27 September, it disappeared, 28th I bought again, 29th I bought AGAIN at 9am, went back to sleep and when I woke up at 11am I had no data. My mobile data was switched off and my background apps are restricted. When I called MTN they told me their system has not updated. I tagged them on Twitter and I assume because that was a public platform, they responded saying I should DM my contacts and query. I did this and I have not been contacted, nor has my data been returned. Also at some point the contact center told me that "the internet" depletes my data, but apparently they can't check from their side. Another thing, I have a fixed contract with MTN, however, in August they deducted more than the fixed amount, when I called to inquire about this I was told I was roaming, same thing happened in September. I don't even know when I was even roaming!