It is in the form of a question, yes. the difference is that if you started the statement with هل, an affirmative inquisitive tool, the question would translate to "Have I written repeatedly about..."
whereas if you use ْأَلَم (a negative inquisitive tool where لم = not, أ = inquisitive article) the question is more accurately translated to "Have I not written repeatedly about...?" and it carries more of an accusatory, preachy tone, you know?