Yes, you need to be switched to the IP4 only range by Ziggo.
This is a customer help customer forum where Ziggo moderators come by almost every working day in every topic.
Make sure that your zip code and house number are in your Ziggo community profile, they cannot be seen publicly, so the correct information can be obtained immediately.
After clicking on the link below, scroll down on the next page: https://community.ziggo.nl/t5/user/myprofilepage/tab/personal-profile:personal-info
Available daily from 8 a.m. to 8 p.m.
1200 free from your Ziggo telephone connection
0900-1884 usual (mobile) call charges
The Chatbox (24 hours a day / 365 days a year) appears at the bottom right of the screen on the page below, as soon as someone is available.