You can use your premium account after canceling until the actual monthly subscription period ends. After this you can use your account with all existing personal playlists and favorites as a free account with its limitations. 

To add to what @Superschlumpf  said , free account is not available in every country so based on where you are living you may / may not have free account option . You can check it below : 

• Argentina

• Bolivia

• Bulgaria

• Chile

• Colombia

• Croatia

• Cyprus

• Egypt

• El Salvador

• Greece

• Guatemala

• Honduras

• Hungary

• Israel

• Kenya

• Mexico

• Nepal

• Paraguay

• Peru

• Philippines

• Poland

• Qatar

• Serbia

• South Africa