I have a straight talk lg premier with a Verizon sim card. The apn settings have been changed vzwinternet and I am receiving and making calls. The internet and mms is also working. But on the status bar I have a 1x instead of 4g and there is also a hollowed out triangle which has something to do with roaming.
your location might help. Honestly I don't think you can use that phone one Version not officially anyway. that might explain your issues. Also which version do you have? You might have the GSM version not the CDMA one.