overpayment by company

I am currently working on a multinational company for 10 months now. We were called for a meeting with the HR department and at the meeting the discussed that they had an error on their payout on our salary. They claim that we "Flex staff" are not entitled to receive allowances and is now reducing our salary by 10% due to the overpayment. They claiming that these allowances are not in our contract which infact is correct but we did not question them for receiving it because we thought it was not stated in the contract and still we were entitled to it because all of us "Flex staff" are receiving the same benefit. Recently we were forced to sign a contract that they would deduct 10% of our salary each month until they recover the overpayment done. The total overpayment they want to recover from me amounts to 31000. Is it even legal for them to recover this amount from its employees? Does the law on diminution of benefits apply here? I have read that there are only 3 reasons on why an employer can deduct according to the labor code..

(a) In cases where the worker is insured with his consent by the employer, and the deduction is to recompense the employer for the amount paid by him as premium on the insurance;
(b) For union dues, in cases where the right of the worker or his union to check-off has been recognized by the employer or authorized in writing by the individual worker concerned; and
(c) In cases where the employer is authorized by law or regulations issued by the Secretary of Labor and Employment.

If they should not be deducting our salaries for their mistake what actions should I take?

Thanks

if it was done in error I think they have the right to recover the over payment.

i agree, the company has the right to recover what was erroneously paid. it would be unjust enrichment on your part to keep that.

tnx sa reply