Disclaimer: this is a very new concept, that also is rapidly changing (20 years ago nobody had a mobile, 10 years ago nobody had a smartphone) you never know how this will be in a year's time. But this is how I currently perceive it (might be quite different for different age and social groups):
- mobieltje used quite a bit, usage this for all mobiles (not just small or cute ones), might be on the return caused by increased usage of the two words below
- mobiel is used less than mobieltje the Netherlands, but I feel usage is increasing
- telefoon, using this not just for a fixed device, but for a mobile as well is increasing I think
- GSM/gsm was used quite a lot up to 5 years ago, it's now on the return
Cell phone is american not english! In australia theyre called mobiles or mobile phones.
Cellphone is short for "cellular telephone" of course there is no difference if you put a space in it or not since it is an abbreviation (technically it should be "Cell. 'phone" but it doesn't matter)