If a phone rings once and then goes to voicemail or rings only briefly, it usually means either that your call is blocked or that the phone is not receiving calls at all. If the phone rings five times and then voicemail picks up, it's more likely that the person on the other end simply isn't picking up the call.
You can also set your Galaxy A series smartphone to record all the calls (or selectively record calls to and from select numbers) automatically without the need to hit the record button. If you frequently record calls, this feature is quite useful, and here’s how you can do it:

Avoid background noise. Whether you have music playing in your office, or you’re sitting in a coffee shop, background noise can make it difficult for your customers to understand your greeting. Limit the noise around you when you leave your voicemail greeting.
There are two steps you have to do before you can use voicemail on your phone. The first is that you have to add a voicemail number. This number varies by country and also your service provider. If you’e use AT&T, you can follow AT&T Galaxy S21 voicemail setting. Open the “Phone” app. Tap the 3 dots on the top right. Tap “Settings“. Tap “Voicemail“. Tap “Voicemail Settings“. Take note of the green number below “Voicemail number“. Go back to the dialer and enter the number from Step 6 (including the *). Press the green phone button. The voicemail number has been set. Return to the Start screen.