Out of Bundle charges.

The company has 2 data sticks on contract which we only use as a backup if the ADSL line is not working. On 12/10/2017 the power was off in City Deep and we ran out of data on the one stick. I contacted Vodacom to request that they add more data to the stick. They refused as I was told they could only top-up the data once I send them an instruction on a signed company letterhead. I explained that it was not possible as the power was off. The person said that the only way they could add data was once they received a written instruction. I ended the call and phoned back later, another consultant advised that I insert the sim-card into a mobile phone and top up the data. Since 27/11/2017 We have been receiving bills for out of bundle usage. Our normal charge for 5g data id R209. For out of bundle charges we were charged R3 348.91 for usage in November, R8 690.08 in December and R33 402.96. Our premises is situated at the Johannesburg Fresh Produce Market. The building is locked at 5pm. We close most days at 3pm and Fridays between 1pm an 3.30pm. The data stich is disconnected daily when we close and locked away in a strong room. We requestedThat Vodacom investigate this matter, but they just reply that everything is correct with their billing. I also requested a copy of our contract for the data stick, but they have not send it to date. The data on second data stick - also 5g is also used up in a day or 2 since last week. We are too scared to go near a computer with the data sticks as we are unable to control the billing. How do we resolve this matter?