import re
regex = r"\b(?:03|7[016])[- /]?\d{3} ?\d{3}\b"
test_str = ("03-123456\n"
"03123456\n"
"03 123 456 \n"
"03 123456\n"
"03/123456\n\n"
"Hi my name is marc and my phone number is 03-123456 and i would like 2 bottles of water 0.5L")
print(re.findall(regex, test_str))
aW1wb3J0IHJlCgpyZWdleCA9IHIiXGIoPzowM3w3WzAxNl0pWy0gL10/XGR7M30gP1xkezN9XGIiCgp0ZXN0X3N0ciA9ICgiMDMtMTIzNDU2XG4iCgkiMDMxMjM0NTZcbiIKCSIwMyAxMjMgNDU2IFxuIgoJIjAzIDEyMzQ1NlxuIgoJIjAzLzEyMzQ1NlxuXG4iCgkiSGkgbXkgbmFtZSBpcyBtYXJjIGFuZCBteSBwaG9uZSBudW1iZXIgaXMgMDMtMTIzNDU2IGFuZCBpIHdvdWxkIGxpa2UgMiBib3R0bGVzIG9mIHdhdGVyIDAuNUwiKQoJCnByaW50KHJlLmZpbmRhbGwocmVnZXgsIHRlc3Rfc3RyKSk=