It will be good if Splynx also add Discount options (like: Customers / Service / Discount on Tariff plans / Internet for advance payment with Pay period, Discount % or Discount Amount with multiple field.
default price of 1 month period is 50$
Discount for 3 month 5% or 2.5%
Discount for 6 month 10% or 5$
Discount for 12 month 20% or 10$