Nighthawk MR1100 Lte issue

I have had the Telestra Netgear MR1100 for more than a year "Working flawless" and 3 days back the internet stopped working and when i checked the WEBUI, i found out that it says "Mobile Broadband disconnected" and when i dug a bit deeper i found out that the LTE is not working but if I leave it on WCDMA the net works ok and that is super slow "i used to get a speed of 70-80 Mbps and now what i am getting is 8Mbps "Very Bad" .

SKU: MR1100-1TLAUS.

FIRMWARE: NTG9X50C_12.06.08.00

I have tried all options available on the net and all not working.  I have swapped my old SIM with a new one and no luck, I have installed a different ISP SIM and it was the same "Nothing Happens" and did a factory reset and Surprisingly the old ISP APN is still their "After a hard reset" ?? I did the reset with the batter and with out the battery.  Did the reset with the SIM and without the SIM, all above did not solve my problem.  I think i have done all that can be done.  Would you look into this and see if a solution is available or shall I throw the piece out !!!