How do I convince my Customer to settle and payup the balance dues for work done ?

As part of my professional services, i was contracted by a Customer to design, create, and publish a marketing video clip for digital marketing efforts of the Customer.

The Customer paid the deposit of 30% on time, but now that the work is fully completed and delivered, the Customer refuses to settle the balance 70% of the dues.

Now the Customer refuses to take my calls,  allow any meetings to discuss the issue, or response to my emails.

I can’t afford to take this matter to court – costly, risky – no guarantees, and time-consuming.

The amount due is not small or insignificant to me, even if it might be to Others.

What can i do to get my payments from this Customer ?