Montenegro mobile internet tip
Among the proposed mobile operators in Montenegro, I tried to use one. Seems like all of them have the same offer, so I just took the office that had no turn. Being a tourist I paid 15 EUR and got 500GB for 30 days. It is a very good offer around Balkans. The best I've seen. Macedonia, Albania and Serbia had many times worse tariffs. As those 30 days passed I extended another 500GB for 30 days with 10 EUR. I made everything at their office. Interestingly they said that I should come exactly after the package finishes in order to get another one. And now another 30 days gone last night, but today is Sunday. No offices are working. However I found that I can top up my balance at a random kiosk. There are many of those. They usually have banners of various mobile operators.
I guess you can get a new SIM card too, but it doesn't make any sense in Montenegro, as in Serbia for example. Here you pay less to extend, and in Serbia you pay more instead. What they do at the kiosk, are sending the money to your balance. But it doesn't mean that the internet will start working right away. In fact if you try to use it, you will loose those 10 EUR in 10 minutes, just by opening some website. So be very careful. I lost 10 this morning, and then we've figured out that we can activate the internet by using a certain telephone code.
This description is for the "One" SIM card. I don't know about others, but should be a siimlar procedure. Before topping the balance up it makes sense to turn the mobile data off. So no internet will be able to leak. Once you have the money on the balance, you need to call *140#. Choose the language by replying with the selected number. Then choose the internet package size. I used L, which is 500GB for 30 days. After that choose the "Description" option. And then you reply with a number from the text (it was 11 in my case) in order to activate the package. Here you go.