Hello! I'm sorry that you're experiencing slow data speed with your Smart unli data 399 plan. Here are some suggestions that you can try to improve your internet connection:
1. Check your signal strength - Poor signal strength can result in slower internet speed. You can try moving to a location with better signal strength or use a signal booster.
2. Clear cache and data - Clearing your phone's cache and data can help improve internet speed.
3. Turn on data saver mode - Data saver mode can help reduce data usage and improve internet speed.
4. Use Wi-Fi whenever possible - If Wi-Fi is available, use it instead of mobile data.
5. Check for network outages - Sometimes, slow internet speed is caused by network outages. You can check if there is a network outage in your area by contacting Smart customer service.
6. Reset your network settings - Resetting your network settings can help improve internet speed.
If none of these suggestions work, you can contact Smart customer service to troubleshoot the issue further.