Do not interrupt
Frequently interrupting customers when they are speaking sends a negative message. It's usually done for one of these reasons:
Source: Sales consultant Joe Takash
– The other person said something that energized you and you just couldn't wait to contribute your idea.
– You disagreed with the customer and were so angry or disturbed by his/her position that you felt compelled to state your own.
– You felt the customer was being long-winded, and you were too impatient to allow him/her to finish.
None of these are valid reasons to interrupt a customer. Whatever you gain by getting your two cents in prematurely, you may lose from a relationship perspective.
You may be making a valid point, but your customer may not appreciate your delivery method.