Since we were going to be in the UK for a month I decided to switch some of my regular Swiss monthly invoicing companies to e-billing so it would be easier to make sure not to miss anything while we were away as we don’t have a printer to use in the UK. Did both our accounts with CSS, well and good, no problems. But for some reason known only to CSS whenever I have a medical invoice with them they send a paper copy through to my hubby even though both accounts are now marked as e-billing. I get the e-billing version as well on our bank account to pay. 
Send them a message in the app and ask them to fix it.
Other than the waste of trees where’s the issue? You’re get the e-bill as well as the paper one so you can still make the payments.