public function setStore($s=null){
        if (file_exists($this->config)){
            include($this->config);
        } else {
            throw new Exception("Config file does not exist!");
        }
        
        if (empty($store) || !is_array($store)) {
            throw new Exception("No stores defined!");
        }
        
        if (!isset($s) && count($store)===1) {
            $s=key($store);
        }
        
        if(array_key_exists($s, $store)){
            $this->storeName = $s;
            if(array_key_exists('merchantId', $store[$s])){
                $this->options['SellerId'] = $store[$s]['merchantId'];
            } else {
                $this->log("Merchant ID is missing!",'Warning');
            }
            if(array_key_exists('keyId', $store[$s])){
                $this->options['AWSAccessKeyId'] = $store[$s]['keyId'];
            } else {
                $this->log("Access Key ID is missing!",'Warning');
            }
            if(!array_key_exists('secretKey', $store[$s])){
                $this->log("Secret Key is missing!",'Warning');
            }
            if (!empty($store[$s]['serviceUrl'])) {
                $this->urlbase = $store[$s]['serviceUrl'];
            }
            if (!empty($store[$s]['MWSAuthToken'])) {
                $this->options['MWSAuthToken'] = $store[$s]['MWSAuthToken'];
            }
            
        } else {
            $this->log("Store $s does not exist!",'Warning');
        }
    }