It has been my experience that you should have at least 2 females for each male. One-on-one usually means that the male will harass the female. Also, your frogs are older than 7 months. It takes about 9 months for the female to mature and about a year for a male. Sexually matured males will have nuptial pads (blackened fingers) and females a swollen cloaca (vent). By the way, both males and females of this species will call. If you listen very carefully, you can hear the males call and the female response. The call of a receptive female is very different from the call of a female that isn't interested in breeding. I have several frogs and the duets are very loud and can be heard all over the house.