From a previous post, 1B1 means that the line is not active or in this case, not available.

Are you dialing a land line phone number or mobile phone number?

011 - 44 - Area Code - Land Phone Number

011 - 44 - 10 Digit Mobile Number

So to dial a UK cell phone number yoy have to dial 011-44-7- their phone number

Is this the format that you're using?

Landlines only use 011-44-number where mobile devices use 011-44-7-number

The phone is definately active as my son can call it from his phone...i am using the correct format...i am english and use to dial this number with no problems. The texts are going through..

Which phone do you have?

There may be settings on the phone which may have been enabled inadvertently. 

I have LG velvet

It just doesnt make sense as i call many english numbers..landlines and cells and they all work except this one

Try to remove her number from your contacts, have her call you, then call her back with the number from call display 

Thank you for the reply...we tried and still hasnt worked.

Check whether Call Forwarding is enabled on your phone or not. The code 1B1 relates to a call forwarding error of some sort.

To check, tap the Phone icon, then tap the menu icon (three dots) in the upper-right corner of the screen. Select Call settings then tap Additional settings. Select Call forwarding and check that Always forward is set to Off.

If you have the Call Forwarding add-on in your self serve account (My Add-ons) you can deactivate call forwarding by dialing #21# from your phones’ dial pad (tap the phone icon to send). Place a call to the phone number in question to see if this resolves the issue.