AT&T seems to be experiencing some issues right now that are leaving customers seeing “SOS” instead of their usual bars of service.

According to The Mobile Report, AT&T has found internally that a failure at a switching center “has resulted in a cascade of problems, including service delays, the inability to provision new SIM cards, and, for many, a complete loss of network connectivity” that may primarily affect iPhones and other Apple devices. Users on Reddit have also reported service issues on some Android devices.

On Tuesday afternoon, there was also a spike in user reports on Downdetector. There has been a dip in reports since the peak, but while writing this article, the Downdetector graph has started to creep up again.

AT&T spokesperson Jim Kimberley tells The Verge that he is looking into what might be going on. Apple didn’t immediately reply to a request for comment.