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Does this happen no matter where you are ?
ie away from your local and surrounding masts.
It maybe worth checking both phones to see if any numbers have found their way into the phones blocking facilities.
Can you try your Sim Card in another phone as a process of elimination to rule out the phone or sim card that may be at fault. Try another Sim in your phone. If necessary any Vodafone Shop can replace the Sim Card via a Sim Swap.
There is some Maintenance Work in your area .....
"We'll be doing some work on our network in this area to improve your calls, texts and data coverage. Sorry if you notice any disruption. We're expecting to start work on 8am 21 Mar 2017 and to have things back to normal by 6pm 24 Mar 2017. Everything else should be working fine.~"
however if this is happening everywhere then the problem(s) could be...
Sim Card issues that any Vodafone Highstreet Store can sim swap to replace the SIM cards.
The phones or phones settings are at issue - checking these settings and or trying another phone can help rule this out.
Customer Services can check your Accounts to ensure nothing is causing this.
Call Plus may be contributing to the problem.
You probably have call plus on your phone but with your partner receiving a new phone, may not have activated the application. Depending on the model of new phone your partner is using, and if the phone came direct from Vodafone the service may be preinstalled.
You can also turn off call and message + and send the texts as normal.
There is further information on the links below.
If there are continued problems, live chat will be able to help.