Questions about imei repairs and issues with the numbers..


I have local pawn type shop and phones are a very good seller. I was having issue buying phones that check out ok when I buy then after 2 weeks or month or so when I am about to sell i check number again and now its blacklisted or have balance. sometime after I sell it customer comes back in few weeks because they activated phone but then it end up on blacklist or finance balance

so I get octopus box to try to fix this problems. Im going to use LG G4 as example

customer comes in with phone I sold them that had good imei at time but now is bad so now I can fix number on LG G4, everything is good. I usually make number change of 1 or 2 digits

then month later for example customer come back say phone no work, there’s a balance or blacklisted because number i used i guess was of other phone since i only changed 1 or 2 digit

so my questions are:

So I think maybe I can put imei of older model like LG G2 but would that work?

if you take lg g4 to store to activate but have a different model imei will this not make problems to activate?

is there a way or method to make good imei fix that don’t get blacklisted or have finance problems later on?

maybe use the unlocked version model of lg g4 imei?

if you can’t post answers here then please pm me
thank you