There's not a specific recovery rom made available by the manufacturer for rollbacks. Do you have any warranty options still on the device?
No, the guarantee has expired. Now I am in Ecuador. I already homologue the phone and it worked very well but when accepting the update B11 by OTA it became brick. But if the manufacturer does not have the rom I do not understand how they installed it to sell it, in addition if they do not give the rom, at least they should provide the key oem of the bootloader, but hey what it is that I no longer have to buy T- Mobile.