"Am receipt of" is not a word, but rather a phrase that means "have received." So, antonyms for this phrase would be words that mean the opposite, such as "have not received" or "are without." Some other antonyms could include "lack," "devoid," "unavailable," or "not in possession of." These words all indicate a state of not having something that one might normally expect to have received. Depending on the context of usage, other antonyms could be applicable, but these examples provide a foundation of alternative meanings that imply the opposite of being in receipt of something.