mm6 code help

First time poster but have been browsing the forums for awhile.......heres my situation. I bought a used s5 on att that I used for 8 months on straight talks network without issue. moved to honduras this week and trying to get my phone set up on Claros network. Found out the phone was locked because of failure to complete contract from previous owner. Att wouldn't let me pay the remainder of previous customer and gave no helpful suggestions so a had a third party swap Imei numbers to a clean unlocked number from a identical phone (s5 sm-g900a) . new number is clean and unlocked but when I put the claro sim in im getting a mm6 code. Data work with the sim card but no phone\text. swapped back in my old sim card(straight talks) and do not get the code and shows bars for cellular. is this something I need to go back to Claro for( trying to make sure because my spanish is very bad and it takes forever to get things done) to update the imei number in their system or is this something I need to go back to the company that did the imei swap? Thanks For any help or direction as to where to go from there.