How do you mean?
If you have an older one and you want to upgrade to a new model, APple will give you 10% of its price towards a new one. However you may be money ahead to simply sell your old one and use the proceeds towards a new one. In the US, Best Buy, AMazon and Walmart - last i knew, would give you store credit for your old device. HOw much depends on the model and condition.
THere are also internet sites like Gazelle that will also give you cash for an old device.
If your device is acting up and may need to be replaced then if it’s under warranty and they determine that it’s a manufacturing defect they can offer you a refurbished replacement. Or if its’ out of warranty then they can offer you the out of warranty replacement which is about 60% of full retail.
Regardless the link below tells you how to wipe your device before you dispose of it