My friend had that with her phone, I text her and then she just kept getting it over and over again. It wasn't a problem with the text I sent, it was a fault on her phone I'm afraid.
Contact her phone provider, they can check things their end and double-check where the fault originates from, and advise her on getting the handset repaired if necessary. BF ended up having hers replaced, but it was only a couple of months before the end of her contract.
My phone does this from time to time. The last time it was so ridiculous (every single flippin message being received countless times for days) that I contacted my network people and they went through lots of technical support over the phone, and couldn't work out why... I was about to send the phone to them as requested when it just suddenly stopped. I didn't send it to them that time because there was a hefty fee to be paid if the problem didn't exist when they received it but as it hsa just started again they are most definitely getting it this time.
One thought the tech guy had was that it was quite an old sim. Apparently they need replacing every couple of years!
Call your network and talk to their technical support and even if the problem goes away for now, then there will be a log of the problem happening this time.
My samsung does the same thing - apparetnly sme makes of samsung phone are notorious for this . All she can do is reset the factpry settings which should sort it out, but she'll lose all her contacts, downloads etc.
It usually takes 3 or 4 days till the repeate texts stop once the first one has been recieved.
Happened to me a few times a couple of months ago (relatively new Samsung smartphone) - got the same messages about 10 or 20 times over nearly a week. What stopped it in the end was deleting the entire message thread, starting with the original. Or maybe they would have stopped anyway, I don't know.
just a thought - do you have a spare phone which could accept that SIM ?
I'm just guessing but if there's a bug where the Samsung seems not to have accepted the text properly, the network will still have a copy and will send it again (and again...) but if the text is accepted by some other handset, and the network can delete it, then hopefully it won't send to the Samsung when the SIM is put back into that phone.
Hope that works, and it should mean that the Samsung will keep all the details and texts that are stored as it will be turned off while the SIM is taken from the Samsung, used in another phone, and then put back into the Samsung...