I have had to take mine back twice, and each time they gave me a new phone.Had a problem with the contrast taking a dip darkening my screen. I also Had a problem with connecting phone calls and getting onto the net.
You need to have a software upgrade (flash) to yout handset. Call 611 from your Nextel press 0 three times to get a live operator. This is a known issue with some early relase i730's that were made in November.