Steps to transfer data contacts from Old Android Phone to OnePlus 5.
Step 1. Make Your Devices Connected
First, connect your Old Android Phone and OnePlus 5 to the computer. Then, launch Mobile Transfer and choose "Phone to Phone Transfer" among the primary page of the software.
Once your devices are connected, Mobile Transfer recognizes and detects both of them. You can see the images of your Old Android Phone in Source and OnePlus 5 in Destination position.
If the position isn't correct, the function of "Flip" can correct it.
Step 2. Select File and Transfer Data
Here, you need to select Contacts, and click "Start Transfer" button to copy contacts data on Old Android Phone. After copying, the data contacts is transferred to OnePlus 5 without any more loss of data.
During the process, please don’t disconnect the devices, or the transfer will fail.
If you want to clear up the data on destiantion device before copying, you can use the "Clear Data before Copy" .