Look at the situation
A Pay As You Go account may hold credit or use a time-limited allowance pack. The two can have different expiry and renewal rules. Ask what funds the next pack and what happens when payment is unavailable.
Read the conditions
Check whether automatic renewal is active. For a seldom-used phone, confirm the required activity to retain the number and set a reminder. Do not assume that receiving occasional messages satisfies an inactivity condition.
Choose the next question
Before going abroad, check activation and travel rules while the phone can still be tested in the UK. Keep account recovery details available without sharing them with a third party.
Keep official confirmation in view.
All explanations here are general guidance. Use your provider’s current instructions and service documents before taking action.
Official reading routes