MIX Telematix ********** customer service

On 31 March 2021 I sent a cancellation email to their dedicated cancellation email to cancel one of my vehicle's tracking devices because I sold the vehicle reference number received: ***7. On the 20th my account was debited. On 01 May I sent another email to both customer care and cancellation email requesting cancellation and received reference number ***1, still no response. Today I sent follow up emails and received reference ***1. I have further called the call center at least 10 times today trying to get this resolved but I keep getting transferred from pillar to post. I had even requested a direct number to the manager in charge of cancellations said to be Samantha ***) who's phone just rings with no answer. I am fed up, I would now like to just cancel all the tracking devices for all my vehicles, the customer services has been absolutely **********, I'd rather have a company that cares to actually attend to my queries!