Keep the conversation going with a call

After a customer has experienced one of your products it is always good to ask for feedback, and one of the best ways is to have an actual conversation with them over the phone.
First, send them an email within the first 30 days and ask if it would be ok for you to call at a time suitable to them. Frame this around asking for feedback.
Offer a promotion at the end like a discount code as a thank you for them taking the time. Showing that you value their feedback, good or bad, could make the difference of them becoming a repeat customer. 
Whatever you do, do not make this call a sales call. They will hang up before you are finished.