It was originally planned to completely abolish the roaming charges in the EU in December 2015. More information about that can be found in an article from last year about roaming prices in the EU. It was finally decided, however, that this will happen in two years time, or in June 2017. Members traveling within the EU will not have to worry about higher charges for calls and text messages beyond the borders of their country.
It should be noted that operators will be able to charge additional fees for excessive usage of the roaming service. Such fees are to be aimed at users who decide to buy a SIM card in a foreign country in order to pay for lower rates than local suppliers of mobile services.
This type of limitation should not apply to people traveling occasionally. However, the exact details are not yet known. It is only known that additional charges for excessive use of roaming services will not exceed, in relation to the prices which are applicable in a given country: 5 cents per minute for calls, 2 cents per SMS and 5 cents per 1 MB of data.
These changes apply only to European Union countries. When travelling to other countries (including Europe) you should always check what are the charges for calls within a given country. You may find useful a detailed statement of Polish international roaming fees because ignorance in the case of international roaming can cost you dearly.