Are you in the US?
I think Wise’s ways of adding funds vary depending on what’s available in terms of payment infrastructure in each country. In the UK where Wise is based, direct debits are very common for routine payments but do not require a card number. But for receiving money Wise UK’s closest equivalent right now is to authorise payment via open banking and your bank ( the newish UK specs for doing this are really good and online here: https://standards.openbanking.org.uk/ )