Shop app buyers keep selecting my local pickup option to bypass shipping charges

[kalelreturns]

So I just started using the Shop app channel and I've already started getting more orders than expected which is nice. However, I've been noticing quiet a few people bypassing my shipping charges by selecting the local pickup option. This is starting to become an annoyance because I have to take the time to reach out to each customer and let them know I have to charge them for shipping if they don't intend on picking up the order from my store. Then I either have to end up canceling the order or have to work up an invoice to send them and make sure they pay it before I ship out the order. 

I'm just curious if anyone else is having this issue and if there is any solution to keep this from happening without having to remove the local pickup option or having to manually send invoices for shipping charges?