01. All room rates are on a room-only basis, exclusive of service charge and taxes.
Note: a room-only basis
03. All elite members enjoy a complimentary room upgrade, subject to availability at check-in.
I want to know if the use of a comma in sentences 01 and 03 IS correct. YES
If yes, why so? : because when two sentences are joined, (as in (02) >(01)), we still have two separate ideas (i) room rates and (ii) (service and tax). This is indicated to the reader by separating them with a comma.
He thinks himself a fool. I agree. >>>
>>> He thinks himself a fool, and I agree.
The two separate ideas are shown as two separate sentences, or joined with the addition of a comma. (Forget what people say that 'a comma indicates a pause'.
NO. It sets apart the different ideas being expressed; and we naturally pause between ideas in our speech, and NOT because there is some invisible comma in our mind acting like a speed bump.
Also, can the article "a" be omitted before the phrase "complimentary room upgrade" : NO