UNFIDNISHED BUILDING BUT NO ANSWERS

we bought a house at Calgro m3 we paid 54 000 deposit me & my partner the structure was finished to be build end of January 2015 but it doesn't have windows, doors, roof & not painted but more than 15 houses around there Ext 4 have been built after our house all of them are finished everything, on February the bank debited the money they say its interests when we query the at Calgro m3 we were told that when the builder put roof on the house there are some interests to be paid but our house doesn't have roof windows door etc when we approach the people responsible at Calgro no one seem to know whats happening they send us pillar to post