I advised a local UX agency owner here in Austin to charge a lot more for her personal time. In this case, $500/hr. She balked, and I pointed out that if it didn't make sense for a certain meeting or certain customer, she could always just discount it on the invoice. That way the baseline is still established and now the customer believes they were given a gift! Even better.
But the larger customers -- or just the ones you don't want to spend that time with -- will have to pay for that.
The high price tag wards away a lot of time -- good! -- and the time that remains is extremely profitable and more likely to actually be needed.
Another thing you could do is have a true partner in the agency, so that you share that title and hopefully share the trust of your customers. Of course that's another can of worms.
If your customers are *wrong* that they need the face-time with you, it's incumbent on you to figure out why they're not trusting your own employees, and whether that mistrust is misplaced.
If they're *right*, you need to ask yourself why you're not employing people who are ask good -- or in fact better -- at their individual jobs than you are (including account management), so that your time can scale.
P.S. The UX consultant make an extra $250k in profit this past 12 months due to this technique.