My sister in law left a property in may 2008 and recieved a final bill for gas and paid in full. We have now recently recieved letter's being threatened with court action for an outstanding amount. She says she's certain it was paid and recieved a letter to confirm but didnt think the need to keep it. Would an SAR be of any use here as would that unearth the letter they sent confirming full payment? It's really stressing her out and the letter she recieved was from csm properties which is apparently in Belfast! The property is in Birmingham! Any help on this would be greatly appreciated

Thanks