Of course, you are completely free to determine your own prices and packages. Combell gives you an amount of MB of webspace, data traffic volume and a certain number of mailboxes.
As long as you do not exceed the limit of your reseller package, you can distribute these quantities as you please between the number of available hosting packages. You can e.g. offer 200 Mb and 5 mailboxes to one client and 345 Mb and 84 mailboxes to another.