Interesting device. An analogue phone on a 1997 car can only be an 'American' problem, though I think that Merc was offering screwed-to-the-car phones even here (Europe) until just a few years ago (maybe even now???).
Whilst we are not quite so restricted as regards handset models, there are limitations. When I took delivery my car in 2001 the cradle could take a whole string of popular Nokia phones, including mine. About a year later I lost it and bought a newer model (the ubiquitous and excellent 6310i), which did not work although it was part of the 6000 range, all of which were supposed to. (My dealer upgraded the software and changed the cradle under warranty....)
The answer must be Bluetooth or something similar, as phone models are proliferating like rabbits, now that the have become a commodity.
DAS
For direct contact replace nospam with schmetterling