Airtime disappearance often

I credited my account worth R10.00, top up on my previous existing balance/ account. I know this is a small amount. On the 6th July., I couldn't go through in purchasing their rush hour bundles as their system for the product was offline with alerts error and time outs! I tried again today the 7th . Is then that I noticed the whole airtime was wiped out. I called customer service line to inquire but got told" I called my vodacom line with same airtime. I don't remember having made a call to myself. I had both units with me. If I mistakenly called my own line, I could have seen from my call history on the alleged call history. I cannot trace any record of the same. Now, I am worried about purchasing high rate on airtime. Secondly, when using rush hour , even if you have outstanding balance on your airtime for next call purchase attempts and you exceed by a second, just know that the balance would be wiped.

I am concern that the administration of airtime is not calculated well by Mtn. Please attend to clarify. Call center advice couldn't make any clear clarity. I didn't call myself. Surely if mtn could be clear on the airtime used I will be considerate.