Tough question, would love any advice people can offer. S4, i9505. Network unlocked. Australia only has three real phone companies with seperate towers - Telstra, Optus, Vodafone (in order of size/popularity) Smaller ISP's exist but resell those companies networks. Tested with heaps of SIM cards - but some simply say "no sim" - cant adjust any APN or carrier settings in the phone as it says insert a SIM card. 1x Telechoice (mine, Telstra reseller) works just fine. Phone owners partner with same company and a sim bought at the same time as mine, does not. 1x regular Telstra worked 1x new SIM from a telstra reseller, did not. 3x optus worked (some resellers, some original) 1x vodafone didnt work (didnt have more than one to test) The phone was telstra branded, but has the least amount of luck working with those. all SIM cards work in every other device i have, only this one phone is being fussy... but the two that arent working belong to the owner of the phone and her partner XD I've tried stock 4.3 (telstra branded), generic 4.4, and echoerom V27 with various modem files. Cleared cache, full wiped in philz, etc. So far i've ruled out the phone as the problem (some sims work) ruled out the sims being the problem (they work in other phones) ruled out the modem and firmware... what the hells left? suggestions are really welcome here, as i need to try SOMETHING.