Regex One Time password mobile phone

Hi, 

I m'a facing an issue, actually I'am trying to update a validation pattern for One Time password mobile phone attribut but I got this error. 

The same regex works with the mobile phone, any idea !!!

Requestor: urn:uuid:7fb2b853-24f0-4498-9534-4e10589723c4
Correlation Identifier: 60551445-a586-4b5a-9df8-d8a0ba736a69
Microsoft.ResourceManagement: Microsoft.ResourceManagement.WebServices.Exceptions.UnwillingToPerformException: Other ---> Procedure: ReRaiseException.  Line number: 37.  Message: A Sql failure occurred.evel 16, State 1, Procedure ReRaiseException, Line 37, Message: Reraised Error 50000, Level 16, State 1, Procedure ReRaiseException, Line 37, Message: Reraised Error 50000, Level 16, State 1, Procedure PostProcessBindingDescriptionUpdate, Line 455, Message: DataAccessSqlException: The attribute StringRegex for attributeTypeDescription object StringRegex cannot be modified since it is a system object..
   --- End of inner exception stack trace ---
   at Microsoft.ResourceManagement.Utilities.ExceptionManager.ThrowException(Exception exception)
   at Microsoft.ResourceManagement.Data.Exception.DataAccessExceptionManager.ThrowException(SqlException innerException, TransactionAndConnectionScope scope)
   at Microsoft.ResourceManagement.Data.DataAccess.ProcessRequest(RequestType request)
   at Microsoft.ResourceManagement.ActionProcessor.ActionDispatcher.ProcessInputRequest(RequestType request)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.ExecuteAction(RequestType request)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.ExecuteAction[ResponseBodyType](RequestType request)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.DispatchRequest[ResponseBodyType](RequestType request, Guid requestIdentifier, Object redispatchSingleInstanceKey, Boolean isRedispatch)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.DispatchRequest[ResponseBodyType](RequestType request)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.DispatchRequest(RequestType request)

Regards