We were involved in a T-bone type accident at highway speeds. I am filing a complaint because I feel Kia Of America did not pursue potential safety issues with the seatbelts. I called them to inform them of the issue to see if there was any other similar trending reports. they stated that they would send an inspector out which they never did. I believe that the seatbelt failed due to the nature of my injuries and discussion with medical experts. I was sitting behind driver. The accident resulted in a fractured sternum and rib injuries, injuries to both of my shins and injury to my coccyx. Most significant is that there was no seatbelt bruising on my chest. All suggestive of hitting back of front seat.I have pix. Also, upon attempting to exit the vehicle post impact, the seatbelt was fully extended, as I got tangled up in it trying to exit. Also to note the drivers seatbelt was fully extended also however they were protected by airbag deployment. The front and rear passenger seatbelts were not extended and those passengers had only minor injuries. My wifes, the driver, injuries were much more serious and has resulted in permanent damage. I contacted Kia of America to report the concern and they assured me they would send an engineer out to provide an inspection. They had multiple months to do this, and I followed up multiple times as to the status of this inspection. During that time the car switched insurance carriers hands however there was ample time to perform the inspection. After a couple months, I followed up again and they informed me that the car was destroyed. I informed them that was not satisfactory and please escalate this. They did and a gentleman called me and left a voicemail. I returned his call 4 times and left voicemails but again no follow up. I feel that this attention to a potentially significant safety issue has been neglected and I ask you to further investigate. I have emails and timelines of conversations documented. Thank you.