on 28-05-2015 11:32
28-05-2015 11:50 - edited 28-05-2015 11:51
I have just checked on the Apple forum and this seems quite common. They suggest resetting your network settings..
ie Settings>General>Reset>Reset Network Settings
on 28-05-2015 12:46
Reset your network as advised above or turn off imessage and reboot phone.
OnePlus 6 (O2 & Sfr), Z3 Tablet (Three UK), iPhone 8+ (EE)