Can I be charged 2 separate HOA fees on 2 lots I purchased and rezoned into one larger lot?

We purchase two lots in a subdivision, one from the builder and one from an individual and had them rezoned into one lot, with our house built in the middle. We have been contacted by email only regarding HOA fees saying we need to pay another $200 for the second lots fees and told if it is not paid a lien will be put on the property. When purchasing/building we were never told we would have to pay for 2 HOA fees. My first question is since it has been rezoned through the city to show as only 1 lot are we responsible for 2 separate HOA fees? If so, is an email a legitimate form of contact for billing? We never received a bill for the second lot/fee. We also have never been notified of any HOA meetings although the email stated there was one last week. If I'm paying HOA fees should I be notified in writing by mail of meetings etc?