Cancelling Vehicle Service Contract After CPO Purchase

I just recently purchased a CPO vehicle and am well within the 30-day full refund day and am in California where by law, I'm allowed to cancel the VSC within 30-days for a used vehicle that didn't come with a manufacturer's warranty. I called in today trying to cancel it and after getting dead end (no one picked up, voicemails left), the Finance Manager finally calls me back (suppose to be his off day so I was told) and tried to persuade me to keep it as I was "putting my money into something useful and not interest" even though the total package which includes 7yr warranty for electronic components (not covered under the CPO Powertrain warranty) and tire/wheels costs me an additional $4000 to finance.

During that time it sounded good, he said for an extra $15/month on a 72 month pay-off plan he could get me onto that Gold-Tier Plan. However, after doing the math, the amount didn't go over more than $1080 so where the heck did the other $3000 go? When I tried to cancel it, he said he would have to rewrite the contract and increase my interest rate back up to where it was originally which was 9.9%. I don't know about you, but that doesn't sound right though I still want to make sure. I have about 3 weeks left to cancel it for a full refund and will probably go through the Third Party Warranty Company that is issuing it to bypass the Finance Manager and cancel it. Any advise would help so i can work this out.