To determine the most cost-effective mobile prefixes for example, 0956 what sim in your region, you'd need to consider various factors such as the local telecom providers, their plans, and the specific benefits they offer (such as free calls within the same network, data packages, international calling rates, etc.). Typically, cost-effectiveness can vary widely based on usage patterns (e.g., voice vs. data, local vs. international calls). Telecom providers often have competitive rates and promotions that change frequently, so it's a good practice to review their current offerings directly on their websites or contact them for the most up-to-date information. Additionally, considering user reviews and asking for recommendations from local communities or forums can provide insights into which prefixes and plans are most advantageous for your specific needs. Since these details are region-specific and subject to change, a direct inquiry to the service providers in your area or a search for recent comparisons online would yield the most accurate and relevant information.