In English spoken countries, the point is used to replace the comma (,).
You should write: 2.7.
You could say: two point seven (BrE). Or two dot seven. (AmE).
However, I somewhat agree to British and American specifications.
The term point is strongly recommended in formal situations, technically speaking.
However, when I traveled abroad, I've heard people using the term dot in their speeches sometimes, due to the speed of the communication. I even dare to say it was because of the habit.
The only real guide is to check on definitions for the context at hand at the time, to pick one that is both known to your target audience.
(if you are aiming at an international audience, depending on the region, one term will be more suitable than other. It is up to you to check it).
I hope I've helped.
(1) Pearson Education. Longman Dicitionary.
(2) Oxford English Advanced Dictionary.
(3) Benson, Donald C., The Moment of Proof: Mathematical Epiphanies, Oxford University Press, USA; New Ed edition (December 14, 2000).