iPhone iphone 4 MMS with question mark error?

[lvigi]

Hello,

i have an iPhone 4, with iOS7.

I am having troubles with MMS, whether they are sent by carrier or imessage. The picture simply says it is downloading, but it never shows. It stays saying it's downloading and after a while, it just appears a blue question mark instead of the picture.

The curious thing is that when my iphone alerts me i have an mms, in the blocked screen i can see the miniature of the picture, but when i open it and go to messages, there appears the question mark or the downloading scene...

I have tried to reinstall the ios, but it doesn't show the pictures.

Anyone can help me?

Thanks in advance.

Lvigi