I’ve watched almost all of the Nosferatu/Dracula films and read Anne Rice’s vampire novels. Some seem to maintain their human lifestyles (old, creepy mansions), while others embrace the changing of the times in order to fit in.
Because vampires can live forever, it is highly doubtful that any intelligent vampire would choose to use an iPhone. Apple rolls out a new product every year, which makes previous generations defunct. An android phone will last much longer.
As for carrying a cell phone while in bat form, wouldn’t it depend on the size of the phone and the bat? I went spelunking once, and we plucked hibernating bats off of the cave walls. They were tiny, about the size of a canary, yet clutched the wall as if their life depended upon it. During a trip to Texas, I spotted a bunch of bats flying around a mall parking lot at night, catching the insects attracted to the lights. The bats were freaking huge. Carrying the weight of a cell phone would not have been a concern; using one while in flight is another matter.
My guess is that any vampire who wants to stay in touch will own one.