I have been sending text and MMS messages to my mums phone and she is not receiving them. I use to have an iPhone and now have a Samsung S5 and the problem still exists, she has a Galaxy 5. The messages I send show as sent on my phone but she never receives them. I am able to receive messages from my mum and we can call each other.
Samsung Galaxy S III GT-I9305
I could send and receive text messages before and after few days I can no longer receive text messages but I can send them. Tested with 2 different phones with 2 different SIM cards but I didn't receive messages from either one.
I don't have any messaging related apps installed apart from Skype which I haven't launched after installation of it.