Data going missing

I have had Vodacom LTE for the past 3 months and data goes missing every month, this month I plugged my device in for the first time on the 9th January 2016, have a data monitoring app on my laptop ]that said I used 138MB the whole day and today I get an email saying i have 6GB left of my 40GB per month limit? <br> Phoned Vodacom on 3 x occasions only to have the call dropped and routed through to their \are you satisfied"<br> I'm going to cancel the LTE from this month as the service is terrible or non existent"""