This month KPN invoice is so much higher than normal

Hello @ADHIKARI1! Welcome, best wishes for 2022 and thank you for your question.

Our monthly invoices always have a second page with a specification of the invoice: you can find your invoices in MijnKPN (your personal KPN page). Does this specification answer your question? 
If not, I think it is a good idea that our Customer Services will check the invoice together with you:

• You can call us on 0800 0402 (this is a free of charge number): from Monday till Friday between  8 and 20 en Saturdays between 8 en 17. Closed on Sundays and public holidays. 
• The same opening hours apply to our chat. You can start a chat on our website   contactpagina. Click on ‘Administratie’ and then on “Ik heb een andere vraag en wil graag contact hebben'. You can start a chat with one of my colleagues by clicking on ‘Naar chat’.
• Or you can fill in your name, Customer number, zipcode and housenumber + the last 3 digits of your bank account in your Forum profile. The data you fill in, is only accesable for KPN moderators. Can you please give a sign here, when you have filled in your data?