The ASA do advertisements. Not sure their relevance.
OFCOM can't punish a network for changing rollout plans. They can't force them to revert to old plans either.
Not sure what would be achieved by contacting OFCOM?
Plans change. Often those changes are due to state aid funding and out of OpenReach's control.
Later surveys can spot issues costing tens of thousands.
Anyone who buys a property based on a single line of text on a website saying "currently in plans" and those plans change, should contact nobody and have a word with themselves.