IMEI in white not READ IMEI

hello a customer brought me a iPhone 6 does not read imei, I made a reballing in MDM9615M since by the little information I've found to be problem that chip that is managed communications and saves the imei and sn . I've seen it sold, but a colleague told me that you have to program them, does anyone know anything about this? I have seen the whole logic board to replace but too expensive and not worth it, I would appreciate help or think that the problem is not that. Already Indicate to me, otherwise the phone works well but in point of sale imei in white and light having no imei not connect the SIM.