The IBI tax (equivelant to council tax) is not determined by how many people are named on the deeds nor does it have anything to do with being non resident. It is a set amount each year based on the Valor Catastral (rateable value) of your property.
The debits that you are seeing could be for your non residents certificate which the Banks organise. This normally is issued covering a period of 2 years.
To clarify the taxes/bills as there seems to be some confusion with terminology:
IBI - Council Tax
Income Tax - If you are non resident you pay income tax even if you do not rent out your property. Additionally, if you rent out your property you pay 24% on any income earned.
Wealth Tax - Now abolished but you still have to complete the relevant tax return. You receive a 100% "credit" which means that you don't actually pay anything.
Basura - Rubbish Tax, usually paid to the local Town Hall
Water - Usually paid every 2 months
Electricity - Now usually paid monthly
Community Fees - Based on the cuota detailed in your deeds
I hope this helps to clarify what needs to be paid
Noreen