This is tough. Writing good advertising/promotional copy is a difficult art. In the following, I've just made a few corrections and suggestions to fix obvious problems. I can't say I like the result enormously.
Welcome to the world of PURE. We assure you that we will prove that your decision to join in the world of PURE and benefit from our many exclusive offers was absolutely right! You will be soaked with exclusive offers. It’s not just another loyalty program, it's all about PURE rewards and earnings. [This is what all loyalty programs offer, so you're not really giving any evidence that it isn't "just another" such program.]
We believe in PURE. PURE is your loyalty towards Popley, and PURE is our relationship with our valued customers like you. Hence We offer you PURE rewards because PURE is our passion to enhance your shopping experience with us. PURE is our commitment to serve you.
If you have any queries or feedback you can directly contact our dedicated Customer Relations Manager at __, dedicated to service you or you can call exclusive the help desk for PURE members at __.
Again, we sincerely appreciate your custom and we hope that this will be the beginning of a long and happy relationship.
Thanks and regards,