What is the ruling on saying "O Allah, I ask You for the good of this call" upon hearing the phone ring and repeating that?

There is no harm in this supplication, and there is no objection to mentioning it and supplicating with it. However, adhering to it with every connection in a way that suggests it is sunnah is not appropriate, as it falls under the category of an additive innovation (bid'ah idafiyyah). But if one says it out of an ill omen or pessimism, then this is reprehensible, and many texts have been narrated prohibiting ill omens.