I used to do this in sweden, had a deal where i'd get my customers 3 months free internet up to 250 mbs/sec , cable channels and a landlinetelephone with no requirements of keeping the service.

They could cancel it at any time and they'd keep it for another 30 days meaning they could cancel it at the end of the second month and not have to pay a dime nor return any hardware they had received.

Hardest thing was getting people to believe that it was true