Q: When my phone is switched off i don't revieve messages

If the phone is off and an SMS is sent to you it should appear when you turn the phone back on. However, this is not true for iMessages.

The problem is probably at the "other" end.  iMessage has a setting to send the message as SMS if iMessage is unavailable (such as when your phone is off).  If the other person is sending you a text from an iPhone (maybe a new or newly upgraded iPhone if this was all working before), and they don't have this selected.  The other person should get a warning message that the message was not sent (but they could have ignored, or missed the message).