Service cancellation

Level 2
Hello, I signed up for ADSL2+ and paid $169.94 (setup + phone line + 1 month service fee + modem delivery). I received an email from TPG saying that they cannot complete the installation due to infrastructure limitation. I was given the option to cancel my account and return the modem for full refund. Do I have to use a particular service provider for the return and will the return delivery be refunded? Thank you.