My iphone 3gs won't receive texts?

My iPhone hasn't been receiving texts for about 9 months now. It used to be that I could just restart my phone and I would receive my texts.
however, this doesn't actually work any more… I have to ask whoever I'm texting to send it again and then I usually receive it twice. Can you suggest anything that will fix it?

Try reseting all network settings. General /reset / network settings then reboot. Also make sure you have the correct settings from your network

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