Terrible customer service

I have been a loyal Cell C customer for many years. More than a week ago I contacted them for my latest invoice as I need to submit it to work as I use my phone for work purposes. I was told it would be in my inbox by the 8 April. When I didn't receive it I called back and was told that it wasn't included and it was their mistake as they forgot to upload it. I also had to wait 2-3 days as they would now escalate it. The next day an agent called to say it would be sent the next day first thing in the morning. It wasn't. I have been struggling now for over a week to get my invoice so I could claim my subsidy. They keep promising it would be sorted out and the team leaders promise to call me back but never do. They are so unprofessional and their customer service sucks but yet they are quick to remind me of my pending debit order and quick to deduct my payment but I cant get a simple invoice out of them.