mike is correct. You should never ask for a radio station by its frequency (e.g. 105.7). What Alexa thinks is on 105.7 might not be the station you want for your area or for the city you indicated.
As Mike stated, it's best to use the station's call letters (usually K-something or W-something). Also keep in mind that some radio stations use nicknames that might not be their true call letters. For example, K-LITE FM in Los Angeles. Their true call letters are KSBL FM. Alexa might know the station if you ask for K-LITE but don't assume that it will play the correct station. If you do get the correct station, you got lucky. Another example. If you ask for KISS FM, there are probably more than a dozen stations nicknamed "kiss". There's KIIS (Los Angeles, CA), KTRS (Casper, WY), WIKS (New Bern, NC), KISN (Belgrade, MT), KZII (Lubbock, TX), and many more. They all call themselves "KISS FM" but their call letters are completely different.
If you are unsure of a station's call letters, you can either call them and ask or look it up on their website. The FCC requires every radio station to have a public inspection file with the station's information.