Data theft

I noticed in January 2016 that my data was being used very fast, more than usual. We installed a programme on all the computers using the data to monitor which one uses the data and to check for a virus. We saw no excessive use of data on any computer and contacted Afrihost to have them check whether the problem is on their side. They refused to discuss this and said there was no problem on their side. We then cancelled our account, but had to give a months notice. I immediately found a new provider and set our router to this new company. On the 1st of Feb, my notice month with Afrihost, we recived new data,20GB, but we are not using that as we have a new provider. Imagine my surprise when I checked my Afrihost data on 2 Feb and saw I only had 623mg left of my 20GB. I retrieved data logs on Afrihost's website and it showed that no logs were made form my line, but yet my data is gone. I logged a new complaint to r solve this th Afrihost on 2 Feb, but they don't seem willing to help.