1. Legally speaking, the neighbours should have collected the maintenance fro the previous owner of the flat,
2. You are supposed to pay the maintenance after being the title holder of the flat & since this payment is not required to be made to govt departments like electricity, Municipality (for property tax) etc., it is not possible for you to ascertain the dues of the previous owner on account of maintenance privately done by other flat owners,
3. While your above arguments are acceptable, it is also a fact that other flat owners have fixed expenses for maintaining all the flats including yours for which they shall have to make payment & if you refuse to pay, they will not be able continue the said maintenance,
4. There are two alternatives left before them. One is to share the dues of the previous owner amongst the other flat owners or to pass on to you since you have purchased the said flat,
5. If you do not pay, nothing will happen to you legally but all other flat owners will certainly go against you,
6. If you are going to stay at your newly purchased flat, it will prudent on your part to pay off the dues of its previous owner on account of maintenance.