Hi, I have a telecom company in the Netherlands so I can explain d]the de]ifferences. A duo or dual sim is a replicated SIM card from your mobile phone number. You cannot use them at the same time because the network doesn't know anymore where to transfer your calls to, to Wich SIM card.
Then ther is the "multisim" or "mb-Verdeler (t-mobile). This is a separate sim card with a separate data number but uses the data from your mobile phone voice contract. KPN is 5 per month just Locke Vodafone and t-mobile is 4 per month.
The last option is the best option if you have enough data.
If you have a company subscription this is in most of the cases possible( unless your employers policy doesn't allow) but provider wise in most cases this is possible.
Using a duo card is strongly advised NOT to use. It's not meant for that purpose. It from an ancient la]ong time ago when cars had own phone systems where you could call with.
If you do not have the multisim possibility, buy a separate data subscription.
You can get 5 gig for 10 euro per m0nth in nl.
Hope this helps,