I have got 8 GB on this month with smarty mobile, if don't use it all does it get roll over to next month or add on to pay plan

With Smarty Mobile, any unused data from your monthly plan does not roll over to the next month. Each month, your plan starts fresh, and any unused data is lost. However, you can keep using your data until the end of your billing cycle, but any left at the end of that period will not carry over. If you have further questions or need specific details about your plan, it's best to check directly with Smarty's customer service or their official website.