Complex sentence: Some rural areas are unlikely ever to be effectively covered since the cost of erecting a cell tower is too high for only a few customers and even in high reception areas it is often found that basements and the interiors of large buildings have poor reception.
Split into simpler sentences: Some rural areas are unlikely ever to be effectively covered since the cost of erecting a cell tower is too high for only a few customers. Even in high reception areas it is often found that basements and the interiors of large buildings have poor reception.