If you have used up your monthly pay as you go limit, you have already received a notification letting you know that pay as you go limit has been reached. If you want to keep using pay as you go, then simply go to settings and increase your monthly limit for pay as you go. Then, just turn your phone data off and then on again. You are good to go.
But remember to keep using internet for the day, your new monthly limit MUST be greater than your previous limit. For example if your previous monthly limit was tk 3, your new limit must be greater than 3.
Please note the maximum amount you can spend on pay as you go for a month is tk 5. Your limit will be refreshed again the first day of every month.