Question 394512
Let m = # minutes , which I will treat as a CONTINUOUS variable (rather than discrete).
Then we want 
0.99 + 0.05m < 0.08m
==> 0.99 < 0.03m
==> 33 < m
Hence for any number of minutes greater than 33 minutes, the 1st phone company is cheaper.  
( Treating m as a discrete variable is actually anti-consumer, because if you spent for example, 25.01 minutes of phone call, then you get charged m = 26 minutes. Would you like that?)