is it possible to sue the company?

[Solarris]

hi all, need help in this matter. my company is a registed singapore company, we have an order placed my an USA company call the Jack Ribbit Collection. the purchase order was to buy leather bags from us. they pay 30% as deposit, 40% when good is delivery and the balance was to be pay after 15 days when goods are received.

this is alright with us, but after we have sent the goods to them and confirm they have received the goods, they total us that they were in a bad cash flow position and wanted us to give them more time to pay up.

we agree to that but it now after 3 months, they still show no sign to pay up the balance, when we call them the person in-charge is either sick or not around, we have leave message for her to contact us but still no answer.

now is there anyway that my company can collect back the balance amount and fine them for late payment or anything.

thanks!