Absolutely this. The splitting up of the rail network is a great example of a break-up of a natural monopoly gone wrong.
For me this is tantamount to mis-selling. They should be renamed from 'Customer Service' to 'TOC Service' because that's exactly who their advice is best for.
I'm quite surprised that there's not yet a train booking website which offers a way of calculating the cheapest ticket - Tickety Split shows that it is possible, and I'd think that any website which guaranteed to offer you the cheapest possible ticket would gain market share very quickly.
https://www.splitticketing.com