The phrase "were on" can be replaced with a variety of words depending on the context. Some synonyms for "were on" could include "engaged," "occupied," "in the midst of," "involved," or "handling." For example, instead of saying "we were on a conference call," one could say "we were engaged in a conference call." Alternatively, instead of saying "I was cooking dinner when the phone rang," one could say "I was occupied with cooking dinner when the phone rang." Using synonyms for "were on" can help to vary your language and make your writing or speech more interesting.