Chosen Solution

After some physical damage. iPhone keep searching for service even if there is no sim card. However, Wifi and Bluetooth works perfectly.

There could be a few reasons for this to occur. ·         Damage to sim tray or its components. ·         Oxidised or missing pads between the board layers. ·         Faulty CPU baseband. For these sorts of repairs you need to have the skills and equipment for microsoldering if not I would suggest sending it to a reputable repairer.