Recently in the last few days I have noticed some times I don't get some of my texts until I connect to the internet.

Saturday my boss texted me, didn't get it until I connected to the internet.
Saturday I texted my dad and he texted back just fine and I had no internet connection.
Today a girl at work texted me, didn't get it until I connected to the internet.
Today I texted my dad and he texted back just fine and I had no internet connection.

Both are on Android, so it can't be iMessage.

Anyone know what the problem could be?