After a lot of help from the guys on the forum, again ..... and thanks, I got it working...... woop woop
For those who need the solution, here it is:
This is what I've done:
New Actions:
Action Name: Premium Member Discount
Action Type -> Add ticket discount
Discount Percentage: 10.0
Action Name: Telecom Thursday Discount
Action Type -> Add ticket discount
Discount Percentage: 7.5
Action Name: No Discount
Action Type -> Add ticket discount
Discount Percentage: 0
Action Name: Remove Discount Tag
Action Type -> Update Ticket Tag
Tag Name: Discount
New Ticket Tag:
Ticket Tag Name: Discount
Do it after ticket selected: Refresh
Sub Tags: Telecom Thursday, Premium Member, No Discount
New Rules:
Rule Name: Premium Member Discount
Event Name: Ticket Tag Selected
Conditions: Tag Name = Discount
Tag Value ? Premium Member
Actions: Premium Member Discount
Rule Name: Telecom Thursday Discount
Event Name: Ticket Tag Selected
Conditions: Tag Name = Discount
Tag Value ? Telecom Thursday
Actions: Telecom Thursday Discount
Rule Name: No Discount
Event Name: Ticket Tag Selected
Conditions: Tag Name = Discount
Tag Value ? No Discount
Actions: No Discount, Remove Ticket Tag
Departments:
Add Discount ticket group to ticket tags in the relevant department you want to use it.