No beating around the bush the answer is no.  No one can gurantee that.  We are always transparent and will not make promises that we cannot keep, we have a very high success rate though.  We will not 100% guarantee anything though as that is not the way SEO works.  We cannot promise you something we do not control.  We have no control over the Search Engines. They could make algorithm changes at any point that could completely change the way SEO is currently known, or theorized to work!  What we can do though is follow the tried and tested practices that are still currently white hat and work as of writing this today.
SEO is a two way relationship though.  That means we work with you in collaboration.  It has to be a two way street to make this work. We can manage everything but if you do not have the budget to do this it is extremely important that you understand the results WILL be affected if you do not for example produce content we have asked for.