this doesn't sound right...if you have four receivers, and didn't have to pay for them, you are most likely renting them...bell never gave away four free receivers, or free rental on four of them for 2 years...besides, even if you went back to cable, if you wanted all your digital channels, you will still need four digital terminals from your cable company.
you should double check your bill, as you are most likely renting the receivers already, so the only increase you should see is the $4...unless you got some secret deal that is special to you, but that is unlikely...and even if that's the case, 4 receivers are $12, and the increase is $4, so that would be $16, not over $30/$35 like you state (unless you have some PVR's or HD receivers in the mix).