Hi,
I also have a Qwest A640 that will shut down about 10 seconRAB into a phone call. The call will be active and the speaker/mic will continue to work 10 or 20 seconRAB after the phone has appeared to shut off, complete with low-battery-warning-phone-turning-off alert and the usual Qwest shutdown animation. I am 100% double-extra-there-could-be-no-doubt-certain that it is not a faulty battery. I suppose it could be a faulty battery interface on the phone, but highly unlikely, and that would be impossible to diagnose and not nearly as interesting.
Here is what I've done up to this point... I have two A640s, one is a qwest, the other is a sprint with ptt. I've successfully switched both to cricket, as well as changed the MSL to 000000. The Sprint A640 works just fine, and a friend used it for a month with no issues.
Neither phone will do a *228 or *22807 with a live ESN. About as soon as it looks like the *228 is working, both phones display an alert:
LOW BATTERY WARNING
Phone Turning Off!
...and then they proceed to turn off. I have tried numerous, fully-charged batteries, so that is prob not the issue. It does this when plugged into a wall charger or a car charger, with or without a battery. I've had this same problem on a couple of Sprint SPH-A680s, a couple Sprint SPH-M300s as well as a couple of Helio Heros(Pantech IM-8300), and that's not a big deal, just one of those quirks with sprint phones we learn to work around. I've had to manually program those phones with the MIN/MDN, and then they all worked just fine.
Well, all except this one Qwest Samsung SPH-A640. It now lives in a big box, with a bunch of other low-rent phones.
Text messaging seemed to work fine though.
I have found no solution to this problem, and I've tried all the obvious, and probably not-so-obvious fixes that I could think of, and believe me, I think of some weird-wacked-out stuff to troubleshoot things.
It would be great to have a .bin firmware file to reflash it, but I have not found one yet, nor even gotten a hint that it exists on the public internet, free or fee.
My advice is to compete for the best A640 destruction video. The winner gets whatever parts survive the destruction.
Jay