Poor return/exchange service

We usually use this company on a regular basis for dog food and they deliveries are always on time and no issues. I bought a jacket for my dog and the sizing charts aren't accurate - fine. But trying to find out how to arrange an exchange is impossible. I left 2 emails on two different days - haven't gotten a response and it's been 4 days now...and one online message - no reply. I then tried to phone the number provided- and it's on voice mail. Their "returns" page "cannot be found". So am I now stuck with a small jacket? I understand that they do not arrange a pick up of good as stated ...but at least tell me how we can go about this exchange (even if I have to make my own delivery arrangements). That's another thing-why don't they provide a return collection service?