Dear Mr. David R.,

Thank you very much for taking over our account with the water company. It came as quite a pleasant surprise when the bill arrived in your name. It is not often we see such kindness from complete strangers these days.

Not to be ungrateful, however, but please be sure also to transfer the address to your own, so that the bills will be sent there and you can pay them.

Thank you again for your generosity.

Insincerely,
Jen