GC interview for parent

[prat8116]

Hello, My sister-in-;law applied for green card for her parent. Now my SIL is going to be out of US for a year or so. Because she (and family are moving overseas ) for a year, she would like to request for postponing her father GC interview at US consulate in India. The interview is for May 2019. She would like to postpone to April 2020. What is the process for doing so, can she call the consulate directly or does she have to email. Please advise

Thanks

[prat8116]

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