Unknown error 0xe8000015

Right, so basically my iPhone 6s plus had full memory storage, and my phone would restart itself, Id then go onto pictures and it would say 0 pictures, but with in 5-10 minutes they had restored back onto my photo library. Anyway, it did this again last night but didn't restore the pictures back, it just signed me out of icloud and wouldn't let me log back in on my phone, so I had no photos until I logged back into icloud. After trying & trying last night I finally called it a night and decided to sleep on it, and thought that my phone would surely allow me to log back in to icloud after having a night to load everything, well it didn't, so I held the menu and power button down at the same time, thinking all it would need was a re-boot, but now won't allow me to activate my phone, the message ''your iPhone could not be activated because the activation server is temporary unavailable. Try connecting your iPhone to iTunes to activate it, or try again in a few minutes'' , & when I plug my phone into my laptop and load up iTunes, the message ''ITunes could not connect to this IPhone, an unknown error occurred (0xE8000015) .. Typical that today is new years day so there isn't anyone available on apple customer help line to help me resolve this issue, so I have been phoneless all day unable to answer new year wishes. Please can someone help. Thank you, Bekka x