A local phone number will increase your conversion rate. When we as consumers look through a webshop and see a foreign number, it sets off a couple of alarming thoughts. 1) This is a foreign webshop, this might not go as easy as it does with a local shop. 2) Do they speak my language if I need to contact them?
 
Having a local phone number will avoid these thoughts and the customer will hopefully continue to the check-out and shortly after be receiving the products.