A Sunni in Iran: When to Start Fasting?
Basically a Muslim should follow the moon sighting of the country he resides in with regard to the beginning of lunar months in general and the beginning of Ramadan in particular.
However, if a Muslim of that country is sure that the authorities there deliberately lie in this regard, which is somehow difficult to be ascertained, then he has to privately follow the moon sighting of the nearest sunni country. In fact, he should consult his sunni fellows there.
There are a sunni minority in Iran and they must have a position regarding such issues.