Turtleneck ok - Shipping deficient

I have together ordered the same to me 3 turtlenecks and realized in the delivery that I had to pay 3 times Porto despite a package. When order was to specify that costs 3.59 and even 3.69 shipping costs are added. I was surprised when I then have a few days later 1 (!) Package in his hand but held 3 (!) Times had to pay postage. How So? The seller's answer and remains incomprehensible for me today. So my conclusion - sweater ok ... Returns deficient!