Unprofessional and bad service

I have had a really bad experience with this provider. First of all I struggled to get them to come onsite and give me a quote. Then I had trouble getting the quote to be sent to me. Then I struggled to get them to come do the installation.

Since installation was done I have had continuous problems with the internet speed based on the the 10gig package I am paying for. I have sent messages to the support whatsapp group that don't get addressed properly. I have sent mail regarding the internet speed test I did with no response from support or owner.

They then have the audacity to call me and ask me to pay the outstanding amount on the installation which I am withholding until the installation is done properly. They inform me that they have cut off my internet until I pay and only then they will assist me.