Could A Child Become Dehydrated If They Are Underfed Due To Insufficient Breast Milk?

Sir/s, my grand daughter born in 17th (3 days back) has been underfed due to insufficient milk from mother. I am scared baby might get dehydrated. Can I call someone and take help. Pl.provide your WhatsApp number, as we are out of Bengaluru. Thanks a tonne !