680 service providers/750P?/new Palm OS

[EBryant]

There's so much I don't know I've been embarassed to ask but, as the list keeps getting longer, now must be better than later so here goes ---

I bought an unlocked crimson Treo 680 and love it except that when I put the Cingular sim card in and tried to make a call, I could barely hear anything even with the volume all the way up and the speaker phone on. I returned the sim card and will be returning the 680 soon but want to know (1) is there is some way I can test for this next time before going through all the hassle?

Next, I intensely dislike Cingular for its prices and unprofessionalism. Getting the same service from Cingular that I now get from Sprint for my 650 will cost at least $25.00 more/month. Among other things, when I got the Cingular sim card for the 680, I was told it had to be returned within 3 business days or I'd have to pay for the entire month which turned out to be false. So (2) can someone tell me what other service provider I can use? Palm has said there's someone on the East Coast -- I'm in California --but they don't know who and T-Mobile told me it sin't supporting the 680 GSM..

Since I'm a Mac person and don't know/understand what I think is called "Open Source" which I guess may somehow enable me to use a Windows based Palm with my Mac, I don't want to wait for the 750 to come out unless I can be sure one running the Palm OS will be available. If one will be, then instead of exchanging the crimson 680 for another one, I'll wait. Question (3) then is: is there expected to be a Palm OS Treo upgrade to the 680 such as a 750P in the near future?

Lastly, I'd like to know more about this new Palm OS that's supposed to be coming out. (4) Will it be compatible with Macs and will the current Palm applications work with it?

Thank you so very much!
Elena