Iphone not sending messages to one contact

[Anonymous]

Well here's the backstory

Had my iphone 3GS for about a year now (on a two year contract)

Never had any real problems with it.

Had to get my sim card replaced recently, so I've got one of these new micro sims from O2 (like the micro sim stuck in the big sim, so it fits my iphone)

I got this replaced this past wednesday.

However thursday evening my phone started playing up

It doesn't seem to be sending messages to one of my contacts

I can still recieve messages from that person, however when I try to reply to them my phone says it has sent the message

However they don't recieve the message

I'm not sure who's problem it might be (I did initally have a problem with regaining network connection on wednesday, until by pure luck I connected my iphone to my laptop and it reactivated...)

But has anyone got any ideas here?

Would reseting my network settings on my phone do anything?

(To clarify, my friend is on a different network, however my phone still sends messages to other contacts on the same network which is odd)

[MI5]

What phone is your friend using? If it's a Samsung it is quite easy to add you to the reject list by accident?

[jonsie]

It's more than likely that the person you can't text has accidentally blocked your number. Ask them to check for blocked numbers in message settings.

[Anonymous]

Some very very very old phone

She broke her HTC and is now using something from before the stone age

I don't know exactly, but to put it one way I could probably kill a large child if I tossed the phone in their general direction

[Anonymous]

I don't think her phone has the ability to block numbers...it's pretty old

But I'll ask her anyway

[MI5]

Maybe if she could try her sim in another phone to see if your texts come through then.....?

[Anonymous]

I'll ask her to do that and see what happens

Just for reference, if that doesn't work any ideas as to what to do next?

[MI5]

Only other thing I can think of is an network error, either with O2 or your friends network.

[Anonymous]

Hmm
Well I'm stumped tbh
As I have other friends on the same network as her, and they're getting my messages....

[jonsie]

All I can suggest at this point is to delete each others contacts in both phones, reboot them and re-enter your contact for each other.