Go to the “Pricing” tab then go to the “Rate Plans” tab.

Click “Edit” in the Rate plan in which you want to make a discount

In the opened settings scroll down.

Then set discounts as shown in the picture below.

If you specify discounts as a percentage, then in the window for a discount, set a percentage of the base price (for example, if you have a 10% discount, then you need to put the figure 90)

If you set a discount in the currency, then you bet on how much the price from the base price will be (for example, the figure 10 is 10 cheaper from the base price)