The color of the line is insignificant. Pregnancy tests can only tell you if you are pregnant. The darkness of the line is no indication of how pregnant you are or how far along you are. You can use the brand tests, even from the same box and get a lighter or darker line any time.
The phantom calls that you have recieved, also known as ghost calls is usually caused by either a poor quality phone line, aka has a high amount of noise or foreign battery due to the line or your on an older copper line.
In most cases, a busy signal simply indicates that the person being called is on the phone, or that the phone is off the hook. In these instances, the signal indicates that there is no technical obstacle to placing the call, but that the call cannot be completed because the phone is in use.