If it’s a new subscription (not an extended contract), you should be able to find a link in one of the welcome emails they sent you. Use this link to activate the card. Otherwise try to call Tele2 with another phone or ask the chatbot for “medewerker spreken” to talk to a support employee.

I used the link as well
Unfortunately the response from account registration page was:
‘Your mobile number is not (yet) known in the system. This could be because your contract is not yet active or is only activated today. Please try again later.’
It was so before the activation date and now it continues to give me the same response.
 

If you got an earlier confirmation that your subscription start at 18-2-2021, the sim should be active. It might be the best that you call customer care monday so they can verify this startdate with you.

Hey @n.yakovenko,
Welcome to the Community and to the Tele2 family! I'm going to help you with your new subscription right away. 

What a beautiful device you've ordered! Of course you want to use your subscription with us as soon as possible. I have taken your details and looked into them. I see you have ordered a new subscription with number portability. That's no problem of course but we will take over your number from your current provider. They have given us a date on which we can port your number. If you want to use your SIM card right now you can, but then you have two subscriptions. I don't know if you want to but if so, please send me the SIM card number in a private message so I can activate it for you. You can also wait and use your old SIM card. 

I like to hear from you! 

Hi @Cas van Tele2 , thank you.
let’s go DM.

@Cas van Tele2 ??