It could just be a network glitch too.
Every time a message is sent to your phone (either SMS or MMS) your phone sends a response back to the network to confirm it's been received.
If the network doesn't receive a response, it will continue to send the message until it does, but in the case of an MMS, if the response sent back doesn't confirm the correct receipt of the message, you will get sent a link to view it online too.
I have no affiliation whatsoever with O2 or any subsidiary companies. Comments posted are entirely of my own opinion. This is not Customer Service so we are unable to help with account specific issues.
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