Mobilephone contracts

Is a verbal contract valid?

Details: My mobilephone contract was about to end and CSL rang me to stitch me up on a 24month contract. I asked them to send me the details but the sales woman spoke poor English and was not clear. They took that as I agreed to the new plan.
After a complaint to CSL, their call centre people listend to the recording and said I agreed BUT I didnt.

1) I did not sign or agree to any contract, so is a voice recording an agreement?
2) Is there a cooling-off period for a contract in HK?

Thanks in advance