Transferring Contacts using Google Sync:

You can use a Google account in order to transfer your contacts from one phone to another. The solution is to sync the contacts stored on the Desire 600 with your Google account, and then re-sync the contacts from the account with the Galaxy Ace 4. To do so:

1. On the HTC Desire 600, log in with your Google account
2. Swipe the "Status" bar down using two fingers
3. Tap "Settings"
4. Scroll to "Personal" and tap "Accounts & sync"
5. Tap "Google" and then choose an account
6. Press "Menu" and then tap "Sync all". NOTE: Alternatively you can clear and mark the check box next to "Contacts" in order to sync contact data
7. On the Samsung Galaxy Ace 4, register the same account that you've used on the Desire 600
8. Go to the apps drawer and tap "Settings"
9. Swipe to "User and Backup" and then tap "Accounts"
10. Press "Menu" and tap "Sync all". Your contacts should now be synced with your Ace 4

Transferring Contacts by Exporting and Importing Them:

Using the "People" and "Contacts" applications that come pre-loaded on the Desire 600 and Ace 4 respectively, you can export the contacts stored on the HTC smartphone in a VCF file, which can then be transferred on the Ace 4 either via email or using a computer. The VCF file can then be imported to the Ace 4's phonebook as explained below:

1. Launch the "People" app on the HTC Desire 600
2. Go to the "People" tab
3. Press "Menu" and tap "Manage contacts"
4. Tap "Import / Export contacts" > "Export to phone storage". Optionally, choose to export to the SD card
5. Select an account and make sure you will recall the VCF file's name before exporting it
6. Tap "OK" to export the file
7. Once exported, open the email app and compose a new mail to attach the VCF file to it
8. Send the email containing the attachment to your own Gmail address
9. On the Samsung Galaxy Ace 4, open the email and download the file
10. Launch the "Contacts" application
11. Press "Menu" and tap "Import / Export"
12. Tap "Import from SD card" / "Storage"
13. Select an account if necessary, and load the downloaded VCF file

NOTE: After the VCF file has been created on the HTC Desire 600, the file can be transferred to the Samsung Galaxy Ace 4 by connecting both smartphones to a computer, and manually copy > pasting the file from the Desire 600's storage to the Galaxy Ace 4's "sdcard" directory. Then, launch the "Contacts" app and import the file as explained above

Using "Send Anywhere":

Last but not least, you can use various third party applications such as "Send Anywhere" in order to transfer your contacts without needing a computer. This app can transfer contacts and various other types of files through a P2P connection, as explained below:

1. Go to the Google Play Store and install "Send Anywhere" on both of your smartphones
2. After the application has been installed, launch it on both devices
3. On the Desire 600, tap "Send" > "Contacts"
4. Select the contacts that you want to share and tap "Send"
5. Finally, choose a method of transfer. By tapping "Generate QR Code" on the HTC device, you can commence the transfer by scanning the resulting code with the Galaxy Ace 4's camera. Alternatively, you can tap "Receive" on the Samsung Galaxy Ace 4, and enter the transfer code from the Desire 600 to begin the transfer