I had the same thing on my recent trip out of state... It started to flash just about as I left NJ and crossed into upstate NY. Very strange, because my verizon phone never indicated any roaming... I dont think Verizon can roam at all, after all they (CDMA) can not switch to any other network, unlike other GSM-based service providers. It stopped flashing after I've crossed back into the NJ on the way back. I found it very annoying, as usually a "flashing" thing requires attention, and I could see it with side vision.

Also, I used to have a "Phone" icon right next to the signal strength indicator. It recently dissapeared, right after taking it to the dealer to install license plates and have it washed by them. I dont think they had any time to do any upgrades to the car's firmware, but at the same time my phone got un-paired, too... Just weird.

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His : 2013 X5 3.5d Deep Sea Blue/Black/Aluminum with ALL packages, 20" 214"s, running boards, Adaptive Drive, Spare Tire, BMW Apps
On Order : 2016 X3 3.5 MSport Silver/Mocha with DHP, CW, Prem, Tech, DA, Lighting

Hers : 2015 328xi MSport Silver/Red

Prior:
2008 X5 4.8
2011 X5 3.5d
2010 335 xDrive
2013 335 xDrive