Buy the Beyond Talk phone. Then do a phone swap from your payLo phone to the Beyond Talk phone. You'll be prompted to change plans.
You can change plans as your needs change as long as your account is active. And you will lose any unused minutes when you switch plans. So it's a good idea to use up all your minutes before you make the switch, according to the Help FAQs. According to the Terms and Conditions:
• Virgin Mobile and payLo accounts are maintained separately. If you switch between a Virgin Mobile service plan and a payLo service plan, your Virgin Mobile or payLo account (as applicable) may be closed and you may be given a new Virgin Mobile or payLo account (as applicable).
• you may switch current service plans, including between Virgin Mobile and payLo. When you switch service plans, you will not receive a refund of any portion of any previously paid service charges and you will lose all of your remaining unused minutes, messages, and data allotment.
• Some service plans are available only on certain phones.
• The payLo plans are only available when setting up a payLo phone from Virgin Mobile USA. None of the payLo phones have Android.
See the current payLo phones at: http://www.virginmobileusa.com/cell-phone-plans/paylo-plans/overview/#overview
• The Beyond Talk plans are only available when setting up a Beyond Talk phone from Virgin Mobile USA.
See the current Beyond Talk phones at: http://www.virginmobileusa.com/cell-phone-plans/beyond-talk-plans/overview/