What mobile phone card is better for traveling in Europe?

The most cost-effective is the cards of local cheap operators, some of which are monthly, such as 20 euros a month. Advantages are cheap and good network speed. The disadvantage is that exceeding the monthly limit will slow down and the procedures will be more troublesome. You may need a local ID card or a long-term residence visa. You can invite local friends to do it! This kind of card is also available, which is more expensive than the local one. But I think it would be better if it was the treasure in buy buy. Please note that the cost of traveling in many countries is different from that of going to only one country.