The term "phonying up" means to create a false or deceitful appearance. The antonyms for this phrase would include words and phrases that convey the opposite meaning, such as being genuine, authentic, sincere, truthful or honest. Some other antonyms that could apply include "keep it real," "be true to oneself," "be natural," or "be transparent." Phonying up implies a degree of artifice or trickery. Its antonyms, on the other hand, describe people or actions that are straightforward, forthright, and without guile. When you choose to be genuine and honest, it allows for more meaningful and positive relationships with others.