you should get a letter from the IRS in 2 to 3 weeks explaining the change. or call IRS
First choose your language.
You should then be transferred to an agent, but there is likely to be a long wait.
You didn't mention if you received a Federal or state refund. If you are getting both, do not go by a total of both refunds. They come separately.
If it was a Federal refund and is "short", did you choose to pay any TurboTax fees out of your Federal refund? Or did you pay the TurboTax fees upfront by credit/debit card?
You appear to be using Online Deluxe Edition, which is $40 for Federal and $40 for state (if applicable). And if you choose to pay out of your Federal refund, there is an additional $40 service fee ($45 for California filers) for that payment option. And also possible sales tax.