Bent Wookie

So I am not really up on my cell phone technology and have tried to read up on things but it's a little confusing... so here's the issue:

Six weeks ago I was in an area with intermittent cell phone service. This included both voice and data. At times, if I drove to a higher area on the road I was able to make calls and get email, surf the web, etc. When I had service, I had both voice and data. I was using a Palm Pre and the Bell network.

A few days ago in the same area, I had zero service. No voice or data. I was not getting any service in the places I did with the Pre. Not until I had almost driven all the way back to civilization, was I able to regain any service. Voice began to work first, but data didn't start until I was pretty well inside the city limits. I was using an HTC Legend on the Bell network.

I checked all the settings on the Legend and ensured everything was activated.

What am I missing here? Why wouldn't the service be, at least, nearly identical. I realize there can be discrepancies between phone reception to an extent, but this was the difference between being on a network and being completely off of it for an extended period of time.

Thanks in advance.