The combination of four columns in two.

[heiner55]

#!/usr/bin/python3
import pandas as pd
import numpy as np

dane=pd.read_csv('calls.csv')

names1 = pd.DataFrame(dane,columns=['Name1', 'Telephone1'])
names1 = names1.rename({'Name1': 'Name', 'Telephone1': 'Tel'}, axis='columns')

names2 = pd.DataFrame(dane,columns=['Name2', 'Telephone2'])
names2 = names2.rename({'Name2': 'Name', 'Telephone2': 'Tel'}, axis='columns')

allnames = pd.concat([names1, names2], ignore_index=True)
print(allnames)