Explanation:
This is another homophone error — something that people hear (but don’t see in print) and make an assumption about based on the sound. Homophone errors are sometimes called eggcorns.

Phrases.org covers “beck and call”:

‘Call’ is used here with its usual meaning. ‘Beck’ is more interesting. The word, although current in English since the 14th century, isn’t one that is found outside the phrase ‘beck and call’ these days. It is merely a shortened form of ‘beckon’, which we do still know well and understand to mean ‘to signal silently, by a nod or motion of the hand or finger, indicating a request or command’.

If the term ‘beck and call’ had originated prior to the 14th century we we would presumably now say ‘beckon and call’.

The Eggcorn Database reports on sightings of beckon call in the wild and further reports that this phrase is also sometimes seen as “beckoned call” and “beacon call.”

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