Not Updating Payment Status

I have paid my full settlement over a week ago. This os after I only was supposed to pay first instalment, I went ahead and settled the full amount.I have emailed this company so many times - however they still have not updated my account to fully paid. As a result their collections department keep on phoning me and threatening me due to non-payment. If I get offended they call me out for being rude. I keep on sending them the proof of payment- yet they keep calling. They have confirmed receipt of payment via email numerous times and promised to update the account- yet every 5 minutes I receive a call from collections threatening me. I have no gone and laid a complaint with the National Credit Regulator as well as the Credit Ombudsman. Perhaps this will shock them back to reality and teach them to actually decently treat their paying customers instead of treating them like pieces of ****.