My church wants to buy some new wireless phones (not cellular, just wireless). We already have a wireless network. Has anyone ever heard of wireless phones and networks interferring? I don't know the frequency of the network, and we haven't picked out a phone yet. I don't even know what the frequencies are nowadays, but I guess we'd want a good one. We also have DSL, but I don't see how that could be a factor.
I've never heard of problems with the two interfering with each other. Even if they use the same band of frequencies they'll just switch channels if any interference does occur and you'd probably never notice it anyway.
The FCC is pretty strict about stuff that transmits not interfering with other stuff.