Im 18 and people still find it hard to differentiate my voice feom a female's over phone calls.. is that normal?

Later in puberty: Voice change in males is dependent on puberty. As a male goes through puberty, the larynx gets bigger and the vocal cords lengthen and thicken, so his voice gets deeper. The completed change may not be noted until the end of puberty which approximately 3-5 years after it starts. For boys who started puberty later, this may carry over into their early 20's.