Difficulties canceling an overpriced contract

I signed up another vehicle and found out that a new contract is almost R100-00 per month cheaper than the old contract. That is approximately R300-00 per month for the vehicles I have on contract now. The lady who assisted me over the phone told me to cancel my contracts and sign up for new contracts and the price will drop.

Tracker's website bombs out when trying to cancel, but all other options are working.