Your sentence is fine and polite as written. I have no grammatical suggestions.
However there may be more diplomatic ways to tell customers that you have included extra charges in the past, but not actually told them about it. This depends entirely on the context.
The general term is charge for costs associated with an item or service. You can charge a customer for the item itself or the service itself, and also charge them additional costs associated with other related expenses.
If you are a company that sends products to people through the mail, then shipping (the cost to send the product) is an expected cost. Sometimes this is referred to as shipping and handling, abbreviated as S&H. It's not uncommon to state the total price for an item, including shipping and handling.
A fee is usually the cost associated with a service of some kind, for example a registration fee, a processing fee, a licensing fee, and so on. Fees may also be penalties for some situation, such as a late fee or a returned check fee. There may be fees associated with the cost of delivering a product, if the delivery requires some kind of special service (an installation fee, for example).
A general way to talk about a document that details the charges in the bill is an itemized bill, or more formally a bill of sale. Less formally you can talk about an itemized receipt, or a breakdown of costs.
So, again as a suggestion:
In the past we included shipping in the total cost of the item, but we have decided to provide an itemized receipt to our customers so they can see a detailed breakdown of the charges.