diff --git a/pkg/sip/service.go b/pkg/sip/service.go
index 239ccb6..6982f3e 100644
--- a/pkg/sip/service.go
+++ b/pkg/sip/service.go
@@ -16,6 +16,8 @@ package sip
 
 import (
 	"context"
+	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/emiago/sipgo"
@@ -36,6 +38,14 @@ type Service struct {
 	mon  *stats.Monitor
 	cli  *Client
 	srv  *Server
+
+	mu               sync.Mutex
+	pendingTransfers map[transferKey]chan struct{}
+}
+
+type transferKey struct {
+	SipCallId  string
+	TransferTo string
 }
 
 func NewService(conf *config.Config, mon *stats.Monitor, log logger.Logger) *Service {
@@ -43,11 +53,12 @@ func NewService(conf *config.Config, mon *stats.Monitor, log logger.Logger) *Ser
 		log = logger.GetLogger()
 	}
 	s := &Service{
-		conf: conf,
-		log:  log,
-		mon:  mon,
-		cli:  NewClient(conf, log, mon),
-		srv:  NewServer(conf, log, mon),
+		conf:             conf,
+		log:              log,
+		mon:              mon,
+		cli:              NewClient(conf, log, mon),
+		srv:              NewServer(conf, log, mon),
+		pendingTransfers: make(map[transferKey]chan struct{}),
 	}
 	return s
 }
@@ -124,35 +135,75 @@ func (s *Service) CreateSIPParticipantAffinity(ctx context.Context, req *rpc.Int
 func (s *Service) TransferSIPParticipant(ctx context.Context, req *rpc.InternalTransferSIPParticipantRequest) (*emptypb.Empty, error) {
 	s.log.Infow("transfering SIP call", "callID", req.SipCallId, "transferTo", req.TransferTo)
 
-	ctx, done := context.WithTimeout(context.WithoutCancel(ctx), 30*time.Second)
-	defer done()
+	var transfetResult atomic.Pointer[error]
+
+	s.mu.Lock()
+	k := transferKey{
+		SipCallId:  req.SipCallId,
+		TransferTo: req.TransferTo,
+	}
+	done, ok := s.pendingTransfers[k]
+	if !ok {
+		done = make(chan struct{})
+		s.pendingTransfers[k] = done
+
+		go func() {
+			ctx, cdone := context.WithTimeout(context.WithoutCancel(ctx), 30*time.Second)
+			defer cdone()
+
+			err := s.processParticipantTransfer(ctx, req.SipCallId, req.TransferTo)
+			transfetResult.Store(&err)
+			close(done)
+
+			s.mu.Lock()
+			delete(s.pendingTransfers, k)
+			s.mu.Unlock()
+		}()
+	} else {
+		s.log.Debugw("repeated request for call transfer", "callID", req.SipCallId, "transferTo", req.TransferTo)
+	}
+	s.mu.Unlock()
+
+	select {
+	case <-done:
+		var err error
+		errPtr := transfetResult.Load()
+		if errPtr != nil {
+			err = *errPtr
+		}
+		return &emptypb.Empty{}, err
+	case <-ctx.Done():
+		return &emptypb.Empty{}, psrpc.NewError(psrpc.Canceled, ctx.Err())
+	}
+}
 
+func (s *Service) processParticipantTransfer(ctx context.Context, callID string, transferTo string) error {
 	// Look for call both in client (outbound) and server (inbound)
 	s.cli.cmu.Lock()
-	out := s.cli.activeCalls[LocalTag(req.SipCallId)]
+	out := s.cli.activeCalls[LocalTag(callID)]
 	s.cli.cmu.Unlock()
 
 	if out != nil {
-		err := out.transferCall(ctx, req.TransferTo)
+		err := out.transferCall(ctx, transferTo)
 		if err != nil {
-			return nil, err
+			return err
 		}
 
-		return &emptypb.Empty{}, nil
+		return nil
 	}
 
 	s.srv.cmu.Lock()
-	in := s.srv.byLocal[LocalTag(req.SipCallId)]
+	in := s.srv.byLocal[LocalTag(callID)]
 	s.srv.cmu.Unlock()
 
 	if in != nil {
-		err := in.transferCall(ctx, req.TransferTo)
+		err := in.transferCall(ctx, transferTo)
 		if err != nil {
-			return nil, err
+			return err
 		}
 
-		return &emptypb.Empty{}, nil
+		return nil
 	}
 
-	return nil, psrpc.NewErrorf(psrpc.NotFound, "unknown call")
+	return psrpc.NewErrorf(psrpc.NotFound, "unknown call")
 }