If you have used up your daily 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 daily 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 daily limit MUST be greater than your previous limit. For example if your previous daily 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 day is tk 5. After tk 5, you will not be able to use pay as you go internet for the day. Your limit will be refreshed the next day again.