Of course it's not possible to verify if the discount can be applied just yet because the iPhone launches in mid-June:
Cingular.com coupon: $25 off cell phones and accessories orders of $25 or more with activation of service, Cingular.com takes $25 off most Cell Phones and accessories orders of $25 or more via coupon code "WLS25". It's the only dollar-off coupon we've seen from Cingular.com. Deal ends July 15.
* found on DEALMAC.COM