I patronized the Krusty Krab once and ordered something very complex. My burger was supposed to contain pickles, which it did. However, I said there were no pickles and asked for (and received) a refund on that basis. Is that a crime?
If you were in washington state, perhaps. It is not criminal fraud, which is limited to impersonation, forgery and various acts related to "instruments". It could be theft, which (RCW 9A.56.020(1)(b)) is
By color or aid of deception to obtain control over the property or services of another or the value thereof, with intent to deprive him or her of such property or services
There has been a lawful transfer of property, then later you gain control over some of their property by aid of deception, and intend to keep the money. What remains to be determined is whether you gained control over their property by "aid of deception", as defined in RCW 9A.56.010. This "means that the deception operated to bring about the obtaining of the property or services; it is not necessary that deception be the sole means of obtaining the property or services" (that much appears to be true), and
"Deception" occurs when an actor knowingly: (a) Creates or confirms another's false impression which the actor knows to be false; or (b) Fails to correct another's impression which the actor previously has created or confirmed
The prosecution would have to prove beyond reasonable doubt that when you made the statement, you did in fact know that the burger contained pickles.
A straightforward fraud
(1) A person who, by any deception, dishonestly—
(a) obtains property belonging to another, or
(b) obtains any financial advantage or causes any financial disadvantage,
is guilty of the offence of fraud.
Maximum penalty—Imprisonment for 10 years.