bad/poor service

i bought 20gb of data at telkom on the 25th of October 2017 split into 10gb night data and 10gb daytime data. On the 29th of October around 5pm I receive an sms say my daytime data has been used up mind you I haven't you my phone the entire day and my data was off. I spoke to Nthabiseng and Clinton from the call centre, they told me on their system it show data usage and the is nothing they can do because the system can not be wrong the problem is with my phone. they can't even tell me what exactly used up the data and on top of that they hang up the phone while im talking.