*THIS IS FOR METRO PCS USERS*FYI I didn't have this problem before the update.Eversince i updated, MM COS13 gave me a Default APN which was INCORRECT!Since the Marshmallow COS13 update I had no LTE signal, I was stuck on "H" or "H+" and even signal dropping every 10 seconds! After days of researching I FINALLY found the solution!:OSettings>Cellular Networks>Preferred network type "LTE". Make sure for " Network operators" you choose your carrier, Most likely it is going to be MetroPCS.Here are the Two APN's you can try, *The Second one worked for me*(Only "APN" & "MMSC" nothing else needs to be changed)1). APN – fast.t-mobile.com MMSC:@@@@@@@@@@@@@@@@@@@@@@@*If those settings don't work out try this one*2). APN– fast.metropcs.com MMSC:If your still having trouble try this:Dial *#*#4636#*#* from your dialerPhone Information>Set preferred network type "LTE/GSM auto (PRL)">Turn Off Radio, Turn it back on>"SMSC" Refresh, Update. Try to also Toggle Airplane Mode Off/On