Cant find out our Hydraqua contract number - help please

Does anyone know a way to get our Hydraqua contract number please? We just pay by direct debit for nearly 20 years - areany of the numbers on thr bank DD the Hydraqua contact no.? Any help would be much appreciated.

I don't know what bank you are with but we are with Caixa.
The online banking has all the bills I've paid in the month listed and, by clicking on the Hidraqua one, it gives me a copy of the bill and the second box along (after the date) is the Hidraqua contract number.

Tjanks Marcliffe = perfect!