Secnum is a mobile application that provides you with a secondary Israeli mobile number on your existing UK SIM card. Developed by Cellact Ltd., this app allows you to make and receive calls and text messages using your new Israeli number, which can also be used to register with messaging services like WhatsApp Business or Telegram.

The app is easy to use and offers various features, including personalizing your ringtone, setting up voicemail, blocking anonymous calls, and managing incoming calls schedule. You can also port your own Israeli number from another operator and use it on the app. Outgoing calls are made through your existing mobile account, according to your agreement with the mobile operator.

Secnum provides a free trial for new users, which includes 10 minutes of call and 10 SMS messages. If you want to continue using the service, you can purchase premium service on Google store. However, please note that the calls are limited only to Israeli numbers and cannot be used to dial premium numbers, abroad, or to the Palestinian Authority.