PAYG customers should receive annual statements that show usage and charges for it, as well as payments made which can be cross-referenced against receipts kept. Also supplier sends a final one also when a PAYG account closes. If Smart Meter not communicating it may then be worth submitting readings when prices change each quarter to inform this annual statement and avoid estimates that end up placing usage in a different quarter to when actually flowed through meter adn credit deducted. There will still be issue of rates not being updated and so credit may be deducted ar rate not making what tariff charges at that time. If Meter is communicating as should then should not be an issue but worth checking rate(s) on meter do make the statement and tariff signed up to