The strait of Hormuz has multiple pathways going through Iranian and Omani waters. Iran is "free" to charge a toll, assuming they are okay throwing out centuries of international law relating to freedom of the seas.
Considering vessels can just transit through Omani waters, what good would charging a fee do? Everyone would just sail on the western and southern side of the strait and traverse freely.
So for the Iranian fees to ever be collected, either Oman would need to charge similar fees (so there is no way around a fee), or Iran would have to attack vessels in Omani territory.
For the record, Oman signed the No Fees/No Tolls pledge with the rest of the EU literally two days ago.
https://www.eeas.europa.eu/eeas/pledge-maintaining-integrity...