Is it possible to connect my cell phone to my amiga to access the internet?
Well.. it depends on a serial cable and possibly by brand.
SonyEricsson/Ericsson (tried with T39/T68/T610 using GPRS) phones works perfectly with Miami and a serial-cable using the built-in serial driver. In fact it is very easy to setup just use Miamiinit and after that just hit connect and of you go. Worked directly for me, no problems whatsoever.
To bad that there is no bluetooth solution available for Amiga though, as that would make phone connections even better.