I have the iPhone 4s with 16g (I have less than a gig left of space) and am on T-Mobile.
Every single time I'm added to a new group text, my phone delays all messages sent to me. Regardless of whether it's another iPhone or if they're on the same carrier as me, none of my messages get to me until an hour or so later.
Is it because I'm low on space? Or is it T-Mobile (probably the worst carrier I've ever had by the way)? Or is it the iPhone software?
Read more:
Why does my iPhone receive messages late when I'm in a group text?