AT&T downplayed the risk of losing its exclusivity agreement for the Apple iPhone in a filing with federal regulators Friday. The iPhone has been AT&T’s best-selling device since it came on the market in 2007.

The device has yet to be released to AT&T’s U.S. rivals since its launch, spurring speculation that subscribers may defect to another carrier once AT&T’s pact with Apple comes to an end. Neither AT&T nor Apple have released details on the length of their exclusivity agreement.

In a quarterly report filed with the SEC, AT&T said the termination of exclusivity agreements would not “have a material negative impact” on profits from its wireless segment but admitted that the loss of the contracts could cause customers to defect to other carriers and reduce net adds.

“Although exclusivity arrangements are important to us, such arrangements may not provide a competitive advantage over time, as the industry continues to introduce new devices and services,” AT&T said.

AT&T’s handset lineup includes about 18 smartphones, including the iPhone. The carrier emphasized the diversity of its handset offerings, saying “offering a wide variety of handsets reduces dependence on any single handset as these products evolve.”