Why does Philips CD4452B/37 DECT 6.0 phone shows “Ext. Call” on incoming call instead of calling number

I have a dual philips CD4452B/37 DECT 6.0 cordless buzz set and the problem is that both the phones show on the screen “Ext. Call” in an incoming call instead of the caller’s name or number. The service is on from my provider as it works on other sets if installed on the same line. I bought the buzz from U.S. and my country of use is India and the buzz doesnt give me the option to change country so i guess the number format could also be the reason. Any help is greatly appreciated??

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