Hi, new to the forum. I have a 6s plus through boost mobile. I seen a few high rating sellers on eBay offering full gsm unlocking. Does anyone have any experience with unlocking a boost/sprint cdma phone to use on any gsm network? If so can I still go back to boost/sprint after unlocking or is only compatible with gsm? Also what is the worst that can happen if I give the eBay seller my imei?