WeSync used to be a great tool for iPhone users to manage contacts on the device. However the developer, Tencent, has removed language support to English and other foreign languages in about Oct 2016. Now if you download WeSync from App store, you will find Chinese is the only language available. We are not sure whether the developer would add extra language packs in future upgrades or not. If you do not know Chinese and would like to batch delete contacts on iPhone you can use its Chinese version and follow instructions below. Alternatively use another address book backup and management app to quickly remove all contacts from iPhone.
Step to step to batch delete iPhone contacts using WeSync Chinese version
Once you have downloaded it from App Store, tap to launch it on iPhone and you will see its home screen like this.

Tap the Menu icon (three horizontal lines) from the top left corner of the WeSync! App, you will open its main menu as shown below.

Choose the first item (Organize Contacts) as shown in above screenshot, you will then open another sub-menu, see below figure.

Tap on the forth item (batch delete contacts) from above menu list, then all your contacts on iPhone will be displayed.

You have two options to select contacts here.
- Select all contacts: simply touch the Select all button (marked as 1 in the above image) at the top right corner to select all iPhone contacts;
- Select multiple contacts: tap the circle before a contact name to select it and repeat to select more contacts. (marked as 2 in the above image)
Once you have selected the contacts you like to remove, touch the Delete button at the bottom right corner (marked as 3 in the above image) to delete them. The contacts will not be deleted immediately. Instead, you will get a prompt as following.

The alert message above means you can’t recover the contacts once being deleted, are you sure to delete them? There are two options beneath. The first one is Cancel, the second one is Confirm. Touch the second option to confirm and allow the app delete all selected contacts from your iPhone instantly.