Winternational.co.uk review for Mailchimp Email SMS Marketing

I have mostly enjoyed using this app and it is very helpful to be able to keep using Mailchimp. However this app has one huge flaw. I have learned after a year of using it, that it unsubscribes your most engaged followers and purchasers when they purchase from your store. That is unless they re-tick your receive emails button. Why would a customer who knows they receive your emails sign up again? I wouldn't do that...we all want smaller inboxes these days and so you would not do it. We use Mailchimp so our customers will have used a double opt in at sign up and they also have an unsubscribe button with each marketing email they receive. I think we cover the issue correctly, so it seems that this is over zealous interpretation of the situation. So as it stands I may lose the ability to contact customers who have previously signed up for our emails because of this system. I have seen other comments on this topic in the reviews. Please help Shopsync, thank you as your app is moslty great but this is really affecting our ability to communicate with regular purchasers and it takes way less money and time and effort to covert someone who has previously purchased from us. We are advised to concentrate on selling to existing customers as well as new ones. Thank you so much!