My phone call spiker not warking

Hi Krishna,

Try cleaning the earpiece speaker grille at the top of the phone; a toothbrush, 90% or higher concentration isopropyl (rubbing) alcohol and some compressed air may help. If not, your speaker may have failed and be in need of replacement. Sad to say iFixit doesn't have a guide to show you how to do that, but there's a Spanish site called Nadie Me Llama Gallina that has just what you need.

Manuales / Samsung Galaxy A21s / Handset

You should be able to find replacement parts easily enough; I usually start with Amazon, eBay and AliExpress. Here's a quick example that should work.

For Samsung Galaxy A21S A217 A325 Ear Earpiece Speaker Replacement Part - AliExpress