请英语高手帮忙翻译一段话,谢谢(汉译英)

at present many companies only compare the samples with their products ,not intending to buy it,so I hope you can pay for the mailing fare(free of sample),and we promise to return the fare once we build the relationship of cooperation

Since some of the factory owners ask for the samples to make comparisons but not actuality purchase the product, it would be great if you can make a payment for the postage(samples remain free),besides we can make a formal promise that this privious payment will be refund in the collaboration afterwards。

As nowadays many manufacturers need samples not to buy actually but to contrast their own product samples, I hope you can pay for the postage(samples were sent for free).and we promise we'll pay back the cost in the future cooperation.