1. I think every person has a mobile phone TODAY, even little children do.( �do � is OK).
2. Lately, mobile phones have become not only a thing THAT is used to call people but a lot more. (Lately is ok but followed by comma).
3. Not so long ago, 30 years back (not to repeat �ago � again), people didn ´t even know what a mobile phone was. (WAS is perfect).
4. In those days people somehow did without smart gadgets. (WELL)
5.There �s no way I want to say that mobile phones are evil. I want to say that the USE of smart devices should be moderate, even more IN THE CASE OF children USE. "Good little by little".
I hope it helps you!! Have a great week!