Services work with the same rule: services should not offer more value than is being paid for.
There is SLAs that measure all the variables your service is measured. The rest is added value you have to play with.
To play with them?
Right, there are services with the unique objective of provide the outputs for what they are created for. If the customer wants more, they have to pay more and cannot be discussion about it.
But there are other services that enables you to generate other type of value for your business and that generates ineterest for other business initiatives that could fit with your service model.
What type of services have you in your portfolio? do you have clear what are the services that provides more value to your customer? Are they well delivered?