Keep getting rejected for sandbox exit on Pinpoint / SNS

Hey everyone... I could not find any documentation on this... so heres what i was wondering...

Upon requesting to exit sandbox for SMS texting... the rejection response i keep on getting says... "your use case would impact the deliverability of our service"...

I am wondering what exactly may cause this decision so i can promptly rectify the issue so i may exit sandbox.

thank you, rob s