If you have ordered a CD from my shop, and is defective, please email me here email@example.com, and let me know what's wrong and I will send a replacement.
For T-Shirts and mugs: there are no refunds for choosing the wrong shirt size- so please check the size chart before ordering a shirt. However- if you ordered a medium, and received a small, for example- then, yes, that IS a reason to receive a refund or replacement. And if the logo is wrong or misprinted on the shirts or mugs? That's a reason for a replacement to be sent to you.
in THAT situation? Don't send the shirt/mug back to me. Instead, take a picture of the item, attach it to an email, tell me what's wrong with the item, then send the email to firstname.lastname@example.org I'll personally take care of it, and a replacement item will be sent to you ASAP.