TDS ON FEE PAID TO NON RESIDENT FOR PUBLISHING (no hard copy) A RESEARCH PAPER IN FOREIGN JOURNAL

I have published a research article in a journal whose head office is located in Switzerland. They sent us an invoice on which my office has deducted 20% TDS  and paid the remaining amount to them. They are now asking remaining 20% payment. The fee paid is called the Article processing charge (APC). The article will be freely available on the internet and no hard copy will be published.