Was Helen Keller completely blind and deaf? And how did she communicate?

Yes, she was completely blind and deaf. It wasn't a birth condition; at nineteen months, she contracted what the doctors then called "brain fever". Modern doctors believe it was scarlet fever or meningitis.

Her educator/companion Anne Sullivan communicated with her through touch and tapping (i.e. put Helen's hand under a pump and then wrote on her hand W.A.T.E.R). Keller then learned how to read Braille and raised lettering and how to write Braille and on an ordinary typewriter.

Keller went to a school for the deaf (with Sullivan) to teach her speech. Her voice became intelligible to those close to her, but never as understandable as the average person.

https://en.wikipedia.org/wiki/Helen_Keller

(Interesting Note: Annie Sullivan was also blind from a disease contracted at a young age. She later had operations and recovered, although never completely.)