Free Installation fee and Router. Then Almost a year later An invoice to pay R1725 Installation Fee

Vumatel is ******** people. Last year September I requested their service as I wanted to have fibre installed in my unit in the complex. I ordered a package online on their website. It was a 20/2mbps Uncapped Fibre package with Firestream as the ISP. This package included free installation/connection and free router. It also included a once off activation fee of R999 and R649 p/m. I moved places in April 2019 and cancelled the service. Now in August, almost a year later, I get an invoice from Vumatel of R1725 outstanding. I also receive a call from a Lulu, requesting payment. There was never an invoice before. As far as my knowledge, everything was sorted and there was no installation fee included. According to my knowledge, all I had to pay for once the activation fee of R999 and a monthly fee of R649, which was paid without fail. Now I'm requested proof of payment for installation, an installation that was supposed to free. This was never part of the deal.