Could it be translated as "Please believe me" since this is a polite request?
It's kind of weird but you have to differentiate 'please' and the politeness of a request. In English a request without 'please' or without softening the phrasing is considered ruder than in Korean. e.g. 'Move back' is considered rude or too direct, whereas 'Please move back' or phrasing as a question is considered more polite ('Could you move back?', 'Are you able to move back?' etc)
It can be confusing because English pretty much has 2 levels of request politeness while Korean has 3, with this being the middle one. So, it's hard to map it to English.
Look at the marker after 나. 를 makes it the object of the verb, whereas 는 would make it the subject.