LTE data gone missing on brand new contract

Got a telkom 20gb data lte contract with modem on the 4/3/2020.That afternoon at just past 4 I open it and plug it in as to get new simcard activated.NO DEVICE connected yet.At 21:00 I get a sms that 19gb data is finished and nothing is still connected to the device.Now when I phone them they just tell me we can only see you used the data which is not possible.We have a uncapped adsl line we use for daily stuff this was suppose to be our backup in case something went wrong like it did the previous month and now they expect me to pay for something I never used?It near impossible to use 19gb data in 5 hours time even when downloading files as it gives me the same speed as my adsl and that takes about 12 hours on a 2gb file.