Custom ROM and kernel developer to add USA frequency bands to my custom phones

This project is for a CUSTOM ROM and kernel expert. I need to add all USA frequency 4g LTE bands to this phone QIN 1s+ so that it works in the USA... It has spreadtrum A53 chip I work directly with the phone factory, so I have all system files for the phones Things to note about the Frequency problems I am having with the phone: 1. AT&T doesn’t recognize it as a 4g phone (but phone calls and text messages works only on HSPA+) 2. T-Mobile recognizes 4g internet but not 4g phone calls This is the phone [https://www.banggood.com/QIN-1S+-VoLTE-4G-Network-Wifi-4G+[login to view URL]]