I need to change the value of params for pageNumber and titulo when i call one of the functions below... but when i call the functions these params remains the same, example

http://miurl.com/jsonapi/views/busqueda_avanzada/informes?page=${this.pageNumber}&views-filter[titulo]=${this.titulo}; //pageNumber returns 0 which is the initial value, but when i call getPage() function still returns 0 when it should return 1 and then 2, for each call. The idea is to create a search filter with Angular. Hope you can give me some clue of what im doing wrong! Thanks

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';

export interface InformesCounter {
  data: any;
  meta: any;
  count: any;
  attributes: any;
  links: any;
  next: any;
  href: any;
  titulo: any;
}

@Injectable({
  providedIn: 'root'
})

export class BuscadorService {
  pageNumber: any = 0;
  titulo: any = '';
  informesNodes =`http://miurl.com/jsonapi/views/busqueda_avanzada/informes?page=${this.pageNumber}&views-filter[titulo]=${this.titulo}`;

  constructor(private http: HttpClient) { }
  
  getNodes(): Observable<InformesCounter> {
    this.pageNumber = 1;
    return this.http.get<InformesCounter>(`${this.informesNodes}`);
  }

  getFiltered(titulo: any): Observable<InformesCounter> {
    this.titulo = titulo;
    this.pageNumber = 1;
    return this.http.get<InformesCounter>(`${this.informesNodes}`);
  }

  getPage(): Observable<InformesCounter> {
    this.pageNumber = this.pageNumber + 1;
    return this.http.get<InformesCounter>(`${this.informesNodes}`);
  }

  ungetPage(): Observable<InformesCounter> {
    this.pageNumber = this.pageNumber - 1;
    return this.http.get<InformesCounter>(`${this.informesNodes}`);
  }

}