If calls keep cutting in and out on your Samsung Galaxy S21, you're not alone. Dozens of Galaxy S21 owners report audio cutouts on Verizon networks, and according to Verizon's tech support, the problem is "widespread." Some AT&T and T-Mobile customers also seem to experience this issue, though not to the degree of Verizon users.

The problem, which affects all three models of the Galaxy S21, appears to stem from the recent June 2022 security update (version G991USQU5CVF1 for Verizon customers). Carriers in the United States began pushing this update on July 6th or July 7th, and customer complaints have only grown in the week since then.

And unfortunately, affected customers probably need to wait for another firmware update. Common solutions, like a SIM card replacement, don't appear to fix audio cutouts on Verizon networks. (Calls through third-party services, such as WhatsApp and Instagram, work fine.)

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I should note that Samsung deleted several user complaints on its forum. But that hasn't stopped customers from making new complaints, often with increasing frustration. This problem affects an impressive number of people, and I'm surprised that neither Samsung nor Verizon have issued an official statement.

Even if you aren't a Verizon customer, I suggest holding out on the June 2022 security update. But that's easier said than done---if you're reading this, there's a good chance you've already installed the new firmware.

Source: Samsung Forum, r/Galaxy S21 (1, 2)