It's a jank, the app is jank, I have been rebooting the app many times, it take more than 2 hours to update

It's a jank, the app is jank, I have been rebooting the app many times, it take more than 2 hours to update. Customer service promised me that they will check the device last week, got sms informing me that case is closed but the device was not checked or repaired. I will not recommend anyone to subscribe with car track, it's a jank. I need to know how can I cancel it, it came with package from taxi SA finance