diff --git a/apps/carrier-connector/internal/rateplan/interface.go b/apps/carrier-connector/internal/rateplan/interface.go
index 4896d08..592b221 100644
--- a/apps/carrier-connector/internal/rateplan/interface.go
+++ b/apps/carrier-connector/internal/rateplan/interface.go
@@ -4,6 +4,36 @@ import (
 	"context"
 )
 
+// Service defines the interface for rate plan business operations
+type Service interface {
+	// Rate Plan operations
+	CreateRatePlan(ctx context.Context, plan *RatePlan) (*RatePlan, error)
+	GetRatePlan(ctx context.Context, id string) (*RatePlan, error)
+	UpdateRatePlan(ctx context.Context, plan *RatePlan) (*RatePlan, error)
+	DeleteRatePlan(ctx context.Context, id string) error
+	ListRatePlans(ctx context.Context, filter *RatePlanFilter) ([]*RatePlan, error)
+	SearchRatePlans(ctx context.Context, criteria SearchCriteria) ([]*RatePlan, error)
+
+	// Subscription operations
+	SubscribeToPlan(ctx context.Context, req *SubscribeRequest) (*RatePlanSubscription, error)
+	GetSubscription(ctx context.Context, id string) (*RatePlanSubscription, error)
+	UpdateSubscription(ctx context.Context, subscription *RatePlanSubscription) (*RatePlanSubscription, error)
+	CancelSubscription(ctx context.Context, subscriptionID string, reason string) error
+	GetActiveSubscription(ctx context.Context, profileID string) (*RatePlanSubscription, error)
+	ListSubscriptions(ctx context.Context, profileID string, filter *SubscriptionFilter) ([]*RatePlanSubscription, error)
+
+	// Usage operations
+	RecordUsage(ctx context.Context, req *RecordUsageRequest) (*RatePlanUsage, error)
+	GetUsage(ctx context.Context, id string) (*RatePlanUsage, error)
+	GetUsageHistory(ctx context.Context, profileID string, limit int) ([]*RatePlanUsage, error)
+	CalculateCost(ctx context.Context, req *CalculateCostRequest) (*RatePlanCostCalculation, error)
+
+	// Analytics operations
+	GetUsageAnalytics(ctx context.Context, filter *UsageAnalyticsFilter) (*UsageAnalytics, error)
+	GetRevenueAnalytics(ctx context.Context, filter *RevenueAnalyticsFilter) (*RevenueAnalytics, error)
+	GetPopularPlans(ctx context.Context, limit int) ([]*RatePlan, error)
+}
+
 // Repository defines the interface for rate plan data operations
 type Repository interface {
 	// Rate Plan operations
diff --git a/apps/carrier-connector/internal/repository/repository_helpers.go b/apps/carrier-connector/internal/repository/repository_helpers.go
index 1570212..9e780f3 100644
--- a/apps/carrier-connector/internal/repository/repository_helpers.go
+++ b/apps/carrier-connector/internal/repository/repository_helpers.go
@@ -9,16 +9,16 @@ import (
 )
 
 // currencyToModel converts currency domain model to database model
-func (r *GormRepository) currencyToModel(currency *currency.Currency) *currency.CurrencyModel {
+func (r *GormRepository) currencyToModel(curr *currency.Currency) *currency.CurrencyModel {
 	return &currency.CurrencyModel{
-		Code:             currency.Code,
-		Name:             currency.Name,
-		Symbol:           currency.Symbol,
-		DecimalPlaces:    currency.DecimalPlaces,
-		IsActive:         currency.IsActive,
-		SupportedRegions: strings.Join(currency.SupportedRegions, ","),
-		CreatedAt:        currency.CreatedAt,
-		UpdatedAt:        currency.UpdatedAt,
+		Code:             curr.Code,
+		Name:             curr.Name,
+		Symbol:           curr.Symbol,
+		DecimalPlaces:    curr.DecimalPlaces,
+		IsActive:         curr.IsActive,
+		SupportedRegions: strings.Join(curr.SupportedRegions, ","),
+		CreatedAt:        curr.CreatedAt,
+		UpdatedAt:        curr.UpdatedAt,
 	}
 }