"I am calling you tomorrow."

Translation: Je vous appelle demain.

[FelipeS.5]

Could we say
"Je t'appelle à demain"?

[aucunLien]

no, 'à demain'' is its own sentence, meaning "see you tomorrow". Works with "à lundi" or "à la semaine prochaine" (see you on Monday/next week) too. It is a very common thing to here or read, so you probably got too familiar with it.

tomorrow=demain

[Reeb155841]

"À demain" is literally "to tomorrow", so can be translated "see you tomorrow". "À plus tard" is "to more late", so "see you later" and "à bientôt" is "to very early", so "see you soon". It helps me to remember :)

[TurianSniper]

Why is this in present tense? Would it be incorrect to use future here?

[BobWells5]

This is incorrect English - "tomorrow" demands the future tense. Or perhaps a capital T for an unusual name.

[miniyazz]

Not necessarily. "I am seeing you tomorrow" is perfectly natural.