Upvote:1
There are no roaming charges in the EU, as of 15/6/2017. Almost.
You can get what you want for 15 Euro.
You can buy a SIM in Copenhagen and roam with it to other EU countries, still enjoying the same terms.
Pitfalls:
See the EU "Roam Like at Home" page
I didn't compare the different offers for Danmark, but a quick Google search gives ID, who take 15 Euro for unlimited calls and 30GB data for 30 days (only 3.3GB while roaming). I'm sure you can find similar offers from other vendors.