I recently received a lump sum of money in my bank account to pay for my mothers funeral and clear her depts that was left, unfortunately a mortgage recovery dept has frozen my account I received a letter from them telling me they will be taking money within seven days. I have never received any other mail in connection with this dept in 6 years. They have never asked to recover this dept before now and I have never received a letter saying that they are taking legal action against me.I can't get a single penny from my account I have 3 kids to support and bills to pay.is what they have done legal and how can I unfreeze my account

Before they can do this they have to have received a judgement against. Ask the bank for a copy of the writ of attachment they received. This will list the docket number and court that issued the judgement. If you never received any notice of this judgement, then you cam move to vacate the judgement on the grounds of improper service. If you can that, it will release the account and you can move the money out.

By the money from your mother's estate should go into an estate account (I assume you are the exector), that will protect it from attachment. You might be able to get that money released because of its source.