C4 Dual won't send SMS

[Clks]

Recently my C5 Dual has stopped allowing me to send SMS messages. I can write one but the button to send, and select which SIM I'm sending from, doesn't become active. I can't figure out if this is a settings issue I haven't been able to figure out?

[MarlonUk1]

can you try to boot in safe mode?

[Clks]

Booted in safe mode and no change...

[Uliwooly]

@Clks

Do you have a data plan?

Is your data on?

Do you have the correct APN settings?

[Clks]

@uliwooly
I've always had a data plan, data working and access to make and receive calls so I'm not sure what you mean by 'the correct' APN settings?

[Uliwooly]

@Clks

Settings > more > internet settings > accept 

[Clks]

@uliwooly accept isn't an option. It says to insert a SIM card even though both sims are working, with service and full signal

[Uliwooly]

@Clks

Is or was the phone locked to a different carrier network? how old are the SIM cards? 

[Clks]

@uliwooly

No. When I first got the phone I could SMS on a 12 month old Thai SIM and a 2 year old UK SIM but now I can't SMS on the UK or brand new US SIM. When I first got it it could text on the UK and Thai SIM cards which is why I assume it must be a setting that I can't work out.

[Uliwooly]

@Clks

Just to clarify, you are trying to use a US SIM card but you are in a different country correct? if so, make sure that you enter the phone number correctly, the same apply to other SIM cards.