# The phone column is currently a string like '-9.994973e+09'
# We use regex to remove everything that isn't a digit
df['phone'] = df['phone'].str.replace(r'\D', '', regex=True)

# We can also truncate or format the resulting string if needed
# For example, keeping only the last 10 digits:
df['phone'] = df['phone'].str.slice(-10)
print(df['phone'])