A new report profiling AT&T’s bandwidth troubles posed by millions of iPhone units reveals that AT&T had Apple modify the handset to ease strain on the company’s network. Per the Wall Street Journal, AT&T Chief Technology Officer John Donovan said he and other executives flew to Apple’s Cupertino, Calif., campus to give the handset maker a “crash course in wireless networking.” With regular return meetings at Apple, AT&T employees helped the iPhone designers create new technologies to limit the strain on the wireless provider.

“Apple rejiggered how its phones communicate with AT&T’s towers,” the report said. “As a result, the phones now put less of a load on the network for such simple tasks as finding the closest tower or checking for available text messages.”

Donovan told the Journal that Apple’s designers are now “in a Master’s class” on networking, having learned the basics and worked with AT&T to improve the iPhone dramatically. Exactly what changes were made, and whether they were hardware or software based, were not revealed.

The article also revealed that AT&T executives set up a 100-day play in December of 2009 to improve the company’s network in large cities where users most commonly experience dropped calls. A random performance test released in February found that AT&T’s 3G network speeds had improved by 84%.

But the Journal also noted Tuesday that AT&T is still “racing” to improve its network as Apple is rumored to be working on a CDMA capable iPhone that could be headed to the Verizon network as soon as this year.