avg price is not affected

I have share of company A is my demat account from last 6 months which . Today I sale share then again bought on same day. But the date of purchase and avg. price is not changed. why?
and if it is intraday trading then what are the charges?

Check this article Will my buy average be affected if I sell shares from my holdings and buy it back the same day?

For brokerage check this What is the brokerage at Zerodha for equity?