The company's policies and rules play a vital role in this contractual agreement.
If you have signed the agreement accepting their terms and conditions (whether you knew them or not), then you are bound by the their terms.
You very clearly say that the company will ban the account of the person who involves in dropshipping using their platform.
You should be aware that the big companies like Amazon does not offer a dropshipping service itself, instead it allows third-party sellers to use its platform to sell products, including utilizing the dropshipping model.
If this company has a clear policy don't allow the dropshipping using their platform then you are at fault for doing thing in contravention to the agreement conditions.
The international company may not risk using the products offered by the persons/company through dropshipping model owing to genuineness of the products which may tarnish their reputation in the market if there is any issue in it.
However yo may approach the company for return of the amount held by them and wait for their reply to decide about further course of legal action.