As a quick fix create a bunch of Outlook Signatures for common / canned responses. Share these with the people helping you on support.
Setup a Support email address that isn't a Mailbox and have it forward to both your Mailbox and whoever is helping you. Make sure the Email setup allows you to easily go in and add/remove forwarding. Do the same for telecoms using a Hunt number or Landline forwarding to a Mobile.
Have a separate sales@ and separate service/sales clearly.
Create a basic flowchart & terminology that determines what is support (and what is not) & define who deals with each type of support incident, what happens when they are not solved etc. Use ITIL terminology.
If you setup or buy a system I would look for these terms/features at minimum:
Problem, Known Error,
Expected outpout, actual output, steps to reproduce
Defects , Requests for Change
Product Backlog, Iteration Number
1st Line,2nd Line,Escalation
Impact Ė H/M/L Urgency - H/M/L
If most calls are users not understanding the functionality you have likely overdeveloped the app, slow down, create a user group or it will become unmanageable
I have built several support centres from scratch, you will benefit from starting out small but right. Read ITIL Service Management, just use the bits that make sense & it will help you design it right from the start.
Users will always be users - you will unlikely change them so its pointless moaning about them, you need to change *YOU* :)