The issue with phones is incredibly controversial as both sides have good points as to why they're both harming and helping social situations. One of the bigger issues, as the question states, is the fact that people become too attached and reliant on their phones, resulting in them becoming less and less social. In some cases, people cant function fully without a phone next to them. The addiction to phones is also at rise, as most can tell by just driving, you'll see quite a few people on their phone while driving.
In short, phones are good and bad, the good being how much they help with basic and complex issues in daily life, and bad being how easily one becomes addicted to the screen time.