native base with a line

I am using native base's item and want to style it such that it has a line. Currently, it's simply invisible. All I can see is the placeholder text and if I change the background color, then I can see that too. But there's no border/line. How can I fix this?

<Input style={styles.newFieldInput}                      onChangeText={handleChange('phoneNumber') as (text: string) => void}                      onBlur={handleBlur('phoneNumber') as (event: any) => void}                      value={values.phoneNumber}                      placeholder="49152901820"                    />

 newFieldInput: {    width: moderateScale(320),    backgroundColor: 'white',  },

I have tried passing in roundedor line as attributes but I get overloading errors as these attributes don't exist on < Input >

Also, is there any way I can add in icon into the beginning of the Input? Or will I necessarily have to wrap it in another component?