CartBot: Gift with purchase

I'M SO HAPPY I FOUND YOU!!! Thank you, thank you, thank you! I've been really struggling to find a solution for my subscription business where I can immediately swap one SKU for another at the point of purchase. My subscription app does product swaps on renewal but I couldn't find anything that would create an immediate swap. It was looking very complicated and costly to do, until I found you! This worked straight away and honestly couldn't have been simpler! I could hug you through the screen! Thank you so much.