If you have an online UC account you can use that to get in touch with the DWP to send messages via your journal. https://www.gov.uk/sign-in-universal-credit
If you don’t have an online account you can use these numbers to contact the DWP:
Telephone: 0800 328 5644
Welsh language: 0800 328 1744
Textphone: 0800 328 1344
Northern Ireland: 0800 012 1331
All lines are open Monday to Friday, 8am to 6pm.