IPhone 4s delayed in message notifications?

Normally every time my phone receives a text I get a push notification and then another 2 minutes later. But recently (the last day or so, on and off) it won't notify me immediately, instead it'll send me a notification with the text but say 58 minutes ago or something, without notifying me straight away. It's really annoying! Just wondering if there's some setting I need to refresh? I've switched my phone on and off a few times but it hasn't changed anything.

My friend also says that he keeps receiving certain messages loads of times and I don't know what's happening haha.

Any advice from iPhone users would be much appreciated:)

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