The potential energy and dipole moment functions of the molecule-ion complex NH3-H-, and its isotopomers, NH3-D- and ND3-H-, have been calculated by the CEPA-2 method. From these functions we have computed the vibration-rotation-inversion states for J=0 and J=1, and the rovibrational transition probabilities between them. The complexes are found to have a nearly rigid structure in the ground state, with the H- or D- ion localized near a hydrogen (or deuterium) atom of the ammonia, and a small probability of tunneling between the three equivalent equilibrium positions. For the vibrationally excited states, however, the probability of this threefold tunneling increases considerably. The umbrella inversion of the ammonia is nearly quenched by the presence of the ion. The character of the rovibrational excitations is determined, and is found to be affected by the isotope substitutions. In order to investigate whether it is possible to evaluate the rovibrational transition probabilities for other total J transitions from the present calculations, an approximate expression for the vibrational transition probabilities has been derived. The formula appears to be valid for the ortho species, for the para species it is found to be rather crude.