No replacement part LG G 4 Motherboard!

Ive had a LG G 4 for 5 months and it started having the Lg admitted \bootloop\" error. I was instructed by Lg call centre to return it to MTN. It was taken and booked for repair assessment 2 weeks ago. On following up with Mtn on numerous occasions as to when i will receive my cellphone, i was told LG has not sent the replacement motherboard. How is this ethical when they, Lg know about the \"bootloop\" issue for a while! LG when will i receive my cellphone? "