AT&T has asked the Federal Communications Commission (FCC) to speed up approval of its waiver to offer WiFi calling on its network, saying T-Mobile and Sprint are already doing so without FCC approval.

AT&T’s legal department complained in a letter to FCC Chairman Tom Wheeler saying AT&T chose to wait for approval while its rivals did not.

AT&T’s lega; Executive Vice President James Cicconi wrote of “a growing concern at AT&T that there is asymmetry in the application of federal regulations to AT&T on one hand and its marketplace competitors on the other,” and this issue “adds fuel to the fire.”

AT&T got into this bind partly because it wanted a waiver from the rules requiring all voice calling services to support teletypewriter devices, which do not operate reliably on WiFi networks. It developed an alternative called real-time text, which was specifically designed to operate on WiFi.

Both T-Mobile and Sprint are advertising their new WiFi calling services, despite a lack of FCC approvals.

AT&T urged the FCC to grant its waiver request without further delay.