I've been through the same experience. Not once, twice.
On both occasions I resigned the instant I discovered the discrepancy. On both occasions the reaction by the companies was to suddenly offer a wage correction. But the disrespect had already been shown in my opinion.
I'm in favour of transparency now. I'm also in favour of clearly understood titles/levels, with knowledge of how to progress and what it means to be at a level (not a hierarchy, but a personal learning progression).
Whether or not this works for non-engineering roles I've yet to find out.