Although the iPhone won’t debut for about a month, it’s already changing the lives of Apple loyalists.

Fans are checking when their current cellphone deals run out – and many are opting for Cingular to be eligible for the iPhone.

“Some have been waiting for years, anticipating last January’s announcement,” says Charles Golvin, Principal Analyst for Forrester Research. “Now they’re looking at their phone contracts to make sure they can switch to the Cingular iPhone service without penalty.”

IPhone users must sign a two-year service contract on Cingular, the only company thus far supporting Apple’s smart phone.

Neither company has disclosed how much the iPhone monthly service will cost, but Cingular’s smart phone plans run as high as $54.99 a month. It seems that, for many customers, paying $500 for the iPhone will be just the beginning.