Lesley Hey Lesley, did you get it sorted?
I just wanted to reach out (as a community member) for you or others who might stumble onto the same problem.
As long as bunq doesn't change how your account is identified or allows you to skip the phone-number and allows you to register with business e-mail only, I am afraid you will have to get an additional phone number.
I wanted to provide you with some options:
Your phone might have eSIM or Dual-Sim slot. In the Netherlands you can get a prepaid eSIM number online in 15 minutes if not quicker.
If you need a physical Simcard, in the Netherlands that could take a business day per mail, or - though I am unsure if this is really wise - you walk in various supermarkets who sometimes sell prepaid sim cards.
Or you can register a 085 voip number as 'landline' and use that as phone-number to register.
You can buy a such a number for 8,95 per year and calling works via voip-apps.
(Heads up, these are referral links)
eSIM:
https://rebrand.ly/tip-esim (includes a discount I believe; switch to tab prepaid after landing if desired, select esim in the form.)
Voip:
https://rebrand.ly/tip-voip
(To mod: If referrals are not allowed, I apologise, you may simply remove the complete last paragraph.)