Cannot send SMS to specific contacts

[zLKidda]

hey, i am having trouble sending text messages to specific contacts. 

i can not send a message to a couple of contacts getting the "Could not send" error 

i can sent messages to others though. i can also receive messages off the people i can not send messages to 

this problem has occurred since i have owned my phone 

any help would be appreciated thanks 

[dm841]

type the number in manually dont use contact's name if it continues reset device by hard reset by holding the power button and volume up together till phpne vibrates 

[zLKidda]

i typed the number in manually and it worked but doing that is so inconvenient and the hard reset did not work  

[dm841]

what network are you on ?

[zLKidda]

O2-uk

[dm841]

call network and tell them the issue they will resolve it