Check the below post:
Issue with Phone Number Pattern Matching Rule — OPN Partner Communities (oracle.com)
I am unable to access that link, Shikha. Any chance that covers adding an ACR for a phone duplicate check? We see many errors due to employees wanting to associate one phone number with multiple phone types (i.e. Work and Work Mobile). We would like to validate that the phone number being added is not a duplicate at the time of entry instead of dealing with the error fallout. Is that possible via ACR?