trait AccountService {
  def debit(no: String, amount: Amount): Kleisli[Future,AccountRepository, Account] = ???
  def credit(no: String, amount: Amount): ReaderT[Future,AccountRepository, Account] = ???
  def transfer(from: String, to: String, amount: Amount) : ReaderT[Future,AccountRepository, (Account,Account)]  = for {
    debitAcc <-  debit(from, amount)
    creditAcc <- credit(to, amount)
  } yield (debitAcc, creditAcc) // If you do not use ReaderT/Kleisli here then you need extra mapping to extract accounts from Try
}

object AccountService extends AccountService

object AccountRepository extends AccountRepositoryInMemory

AccountService.transfer("from", "to", 10).run(AccountRepository)